diff --git a/GUI/CommonWidgets/DesignerHelper.cpp b/GUI/CommonWidgets/DesignerHelper.cpp
index 296234761833e5e0f426d92e552126c4d5272b2b..55d4006838aa5d7c38afee1621f77817fce1d3e5 100644
--- a/GUI/CommonWidgets/DesignerHelper.cpp
+++ b/GUI/CommonWidgets/DesignerHelper.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/CommonWidgets/DesignerHelper.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include <QPainter>
 #include <cmath>
diff --git a/GUI/CommonWidgets/ItemSelectorWidget.cpp b/GUI/CommonWidgets/ItemSelectorWidget.cpp
index 22d4ea26578659c5fc907a6753db9ebde9d6df47..34ec83badf94398b747f441dcb059bedaeb3935f 100644
--- a/GUI/CommonWidgets/ItemSelectorWidget.cpp
+++ b/GUI/CommonWidgets/ItemSelectorWidget.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/CommonWidgets/ItemSelectorWidget.h"
-#include "GUI/Session/SessionDecorationModel.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionDecorationModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/utils/mainwindow_constants.h"
 #include <QListView>
 #include <QVBoxLayout>
diff --git a/GUI/CommonWidgets/ItemStackWidget.cpp b/GUI/CommonWidgets/ItemStackWidget.cpp
index 83d0f0b8e1883b622ef71e53b303bd96515de5b0..5f2d03d8cbd420cde1f8cfdbeb76acbf153f30b4 100644
--- a/GUI/CommonWidgets/ItemStackWidget.cpp
+++ b/GUI/CommonWidgets/ItemStackWidget.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/CommonWidgets/ItemStackWidget.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include <QStackedWidget>
 #include <QVBoxLayout>
 
diff --git a/GUI/CommonWidgets/ModelTreeView.cpp b/GUI/CommonWidgets/ModelTreeView.cpp
index 323194aba0721c51ffecf8b1b6604cb293cbd9e4..5d2ce512835832a2e4ec4cc24c96240814e3bec6 100644
--- a/GUI/CommonWidgets/ModelTreeView.cpp
+++ b/GUI/CommonWidgets/ModelTreeView.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/CommonWidgets/ModelTreeView.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/SessionDecorationModel.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionDecorationModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include <QTreeView>
 #include <QVBoxLayout>
diff --git a/GUI/CommonWidgets/SessionItemController.cpp b/GUI/CommonWidgets/SessionItemController.cpp
index 5abd0b043dda10d3746b2c28844eda3fbf10aa4f..04e05349385d55d80242ab177ad5af9ba56bc875 100644
--- a/GUI/CommonWidgets/SessionItemController.cpp
+++ b/GUI/CommonWidgets/SessionItemController.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/CommonWidgets/SessionItemController.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 SessionItemController::SessionItemController(QObject* prt)
     : QObject(prt), m_item(nullptr), m_parent_subscribed(false)
diff --git a/GUI/DataLoaders/AutomaticDataLoader1D.cpp b/GUI/DataLoaders/AutomaticDataLoader1D.cpp
index 31e993fe009b52120a2a8c5ce751db317c5aad22..dc0d9eb3759fc09cdd2faa5ee4c86af4b355d52f 100644
--- a/GUI/DataLoaders/AutomaticDataLoader1D.cpp
+++ b/GUI/DataLoaders/AutomaticDataLoader1D.cpp
@@ -16,8 +16,8 @@
 #include "Device/InputOutput/OutputDataReadReflectometry.h"
 #include "GUI/DataLoaders/AutomaticDataLoader1DResultModel.h"
 #include "GUI/Models/Data/ImportDataInfo.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/utils/DeserializationException.h"
 
 QString AutomaticDataLoader1D::name() const
diff --git a/GUI/DataLoaders/AutomaticDataLoader1DResultModel.cpp b/GUI/DataLoaders/AutomaticDataLoader1DResultModel.cpp
index aef777caa7fb2edb81b0a95c1c545cb7065d447b..871a66583316c2a831aaf12d60bc387c1e6840fb 100644
--- a/GUI/DataLoaders/AutomaticDataLoader1DResultModel.cpp
+++ b/GUI/DataLoaders/AutomaticDataLoader1DResultModel.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/DataLoaders/AutomaticDataLoader1DResultModel.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 
 AutomaticDataLoader1DResultModel::AutomaticDataLoader1DResultModel(RealDataItem* item)
     : m_item(item)
diff --git a/GUI/DataLoaders/QREDataLoader.cpp b/GUI/DataLoaders/QREDataLoader.cpp
index 7da290372ce494de90b67016609ebcde918bcb07..87415751e0dfe2b5eace102bd6cc61d30b522252 100644
--- a/GUI/DataLoaders/QREDataLoader.cpp
+++ b/GUI/DataLoaders/QREDataLoader.cpp
@@ -17,9 +17,9 @@
 #include "Device/Coord/AxisNames.h"
 #include "GUI/DataLoaders/QREDataLoaderProperties.h"
 #include "GUI/DataLoaders/QREDataLoaderResultModel.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/utils/DeserializationException.h"
 #include "ui_QREDataLoaderProperties.h"
 #include <QFile>
diff --git a/GUI/Session/AxesItems.cpp b/GUI/Items/AxesItems.cpp
similarity index 98%
rename from GUI/Session/AxesItems.cpp
rename to GUI/Items/AxesItems.cpp
index 802d8ea3b667b27f43f0f045d398cb95c474518b..4073bf7e7e536399e9d5818ef4cfb176ff84d69e 100644
--- a/GUI/Session/AxesItems.cpp
+++ b/GUI/Items/AxesItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/AxesItems.cpp
+//! @file      GUI/Items/AxesItems.cpp
 //! @brief     Implements various axis items
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 #include "Base/Axis/FixedBinAxis.h"
 
 const int max_detector_pixels = 65536;
diff --git a/GUI/Session/AxesItems.h b/GUI/Items/AxesItems.h
similarity index 92%
rename from GUI/Session/AxesItems.h
rename to GUI/Items/AxesItems.h
index 7cfd047053a57cc537d427c6c6495241527620f0..c173cfa10b8dc3c182a14cf8f37d1fb60874ebba 100644
--- a/GUI/Session/AxesItems.h
+++ b/GUI/Items/AxesItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/AxesItems.h
+//! @file      GUI/Items/AxesItems.h
 //! @brief     Defines various axis items
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_AXESITEMS_H
-#define BORNAGAIN_GUI_SESSION_AXESITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_AXESITEMS_H
+#define BORNAGAIN_GUI_ITEMS_AXESITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <memory>
 
 class IAxis;
@@ -89,4 +89,4 @@ private:
     void setMinMaxEditor(const QString& editorType);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_AXESITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_AXESITEMS_H
diff --git a/GUI/Session/BackgroundItems.cpp b/GUI/Items/BackgroundItems.cpp
similarity index 95%
rename from GUI/Session/BackgroundItems.cpp
rename to GUI/Items/BackgroundItems.cpp
index 866945bcd1d75264d1418a063719118e16c73eb3..842c8c0f8908ec5a40ea42304a4c2e080ba7cf03 100644
--- a/GUI/Session/BackgroundItems.cpp
+++ b/GUI/Items/BackgroundItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BackgroundItems.cpp
+//! @file      GUI/Items/BackgroundItems.cpp
 //! @brief     Implements BackgroundItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/BackgroundItems.h"
+#include "GUI/Items/BackgroundItems.h"
 #include "Core/Background/ConstantBackground.h"
 #include "Core/Background/PoissonNoiseBackground.h"
 
diff --git a/GUI/Session/BackgroundItems.h b/GUI/Items/BackgroundItems.h
similarity index 87%
rename from GUI/Session/BackgroundItems.h
rename to GUI/Items/BackgroundItems.h
index 7a91ec36abf69be201aa0de6ee75b387895890f2..b8507d68c71cd9d04ee15d50ed22b6cc9c228b77 100644
--- a/GUI/Session/BackgroundItems.h
+++ b/GUI/Items/BackgroundItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BackgroundItems.h
+//! @file      GUI/Items/BackgroundItems.h
 //! @brief     Defines BackgroundItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_BACKGROUNDITEMS_H
-#define BORNAGAIN_GUI_SESSION_BACKGROUNDITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_BACKGROUNDITEMS_H
+#define BORNAGAIN_GUI_ITEMS_BACKGROUNDITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IBackground;
 
@@ -56,4 +56,4 @@ public:
     std::unique_ptr<IBackground> createBackground() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_BACKGROUNDITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_BACKGROUNDITEMS_H
diff --git a/GUI/Session/BeamAngleItems.cpp b/GUI/Items/BeamAngleItems.cpp
similarity index 96%
rename from GUI/Session/BeamAngleItems.cpp
rename to GUI/Items/BeamAngleItems.cpp
index 643b4392d5b62f96886caf9eb4c8639d6c6173f3..f1f2a87b24f5254b1140f577cd3fb51a4047f648 100644
--- a/GUI/Session/BeamAngleItems.cpp
+++ b/GUI/Items/BeamAngleItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamAngleItems.cpp
+//! @file      GUI/Items/BeamAngleItems.cpp
 //! @brief     Implements class BeamAngleItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/BeamAngleItems.h"
+#include "GUI/Items/BeamAngleItems.h"
 #include "Base/Const/Units.h"
 
 BeamAzimuthalAngleItem::BeamAzimuthalAngleItem() : BeamDistributionItem(M_TYPE, m_show_mean)
diff --git a/GUI/Session/BeamAngleItems.h b/GUI/Items/BeamAngleItems.h
similarity index 83%
rename from GUI/Session/BeamAngleItems.h
rename to GUI/Items/BeamAngleItems.h
index 751bc7a564956e2bb4269afaf6102439a581b271..eb1a3c19ba5d5774ea82809d6f9b054e56e75ae4 100644
--- a/GUI/Session/BeamAngleItems.h
+++ b/GUI/Items/BeamAngleItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamAngleItems.h
+//! @file      GUI/Items/BeamAngleItems.h
 //! @brief     Defines class BeamAngleItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_BEAMANGLEITEMS_H
-#define BORNAGAIN_GUI_SESSION_BEAMANGLEITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_BEAMANGLEITEMS_H
+#define BORNAGAIN_GUI_ITEMS_BEAMANGLEITEMS_H
 
-#include "GUI/Session/BeamDistributionItem.h"
+#include "GUI/Items/BeamDistributionItem.h"
 
 class BeamAzimuthalAngleItem : public BeamDistributionItem {
 public:
@@ -45,4 +45,4 @@ private:
     static const bool m_show_mean = true;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_BEAMANGLEITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_BEAMANGLEITEMS_H
diff --git a/GUI/Session/BeamDistributionItem.cpp b/GUI/Items/BeamDistributionItem.cpp
similarity index 97%
rename from GUI/Session/BeamDistributionItem.cpp
rename to GUI/Items/BeamDistributionItem.cpp
index c63327c4ebecbe60ea40ade67acc266874c07089..3627ae213fb0e9ea3e88700bf9437680ec41f0e2 100644
--- a/GUI/Session/BeamDistributionItem.cpp
+++ b/GUI/Items/BeamDistributionItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamDistributionItem.cpp
+//! @file      GUI/Items/BeamDistributionItem.cpp
 //! @brief     Implements class BeamDistributionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/BeamDistributionItem.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/RealLimitsItems.h"
+#include "GUI/Items/BeamDistributionItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/RealLimitsItems.h"
 #include "Param/Distrib/Distributions.h"
 
 namespace {
diff --git a/GUI/Session/BeamDistributionItem.h b/GUI/Items/BeamDistributionItem.h
similarity index 86%
rename from GUI/Session/BeamDistributionItem.h
rename to GUI/Items/BeamDistributionItem.h
index 6c54ad48099e338fca24a899e151bc31bc835667..01b644101c07c0bd4736c529b4cc07c209e7bec4 100644
--- a/GUI/Session/BeamDistributionItem.h
+++ b/GUI/Items/BeamDistributionItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamDistributionItem.h
+//! @file      GUI/Items/BeamDistributionItem.h
 //! @brief     Defines class BeamDistributionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_BEAMDISTRIBUTIONITEM_H
-#define BORNAGAIN_GUI_SESSION_BEAMDISTRIBUTIONITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_BEAMDISTRIBUTIONITEM_H
+#define BORNAGAIN_GUI_ITEMS_BEAMDISTRIBUTIONITEM_H
 
-#include "GUI/Session/DistributionItems.h"
-#include "GUI/Session/ItemWithDistribution.h"
+#include "GUI/Items/DistributionItems.h"
+#include "GUI/Items/ItemWithDistribution.h"
 #include "Param/Distrib/ParameterDistribution.h"
 
 //! The BeamDistributionItem handles wavelength, inclination and azimuthal parameter
@@ -59,4 +59,4 @@ template <typename T> T* BeamDistributionItem::setDistributionType()
     return setGroupPropertyType<T>(P_DISTRIBUTION);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_BEAMDISTRIBUTIONITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_BEAMDISTRIBUTIONITEM_H
diff --git a/GUI/Session/BeamItems.cpp b/GUI/Items/BeamItems.cpp
similarity index 96%
rename from GUI/Session/BeamItems.cpp
rename to GUI/Items/BeamItems.cpp
index 657613d93041ac9f203066dad5920e2d3d36025d..d7928d0cd1aba705ae68020bacea0c1000105f8c 100644
--- a/GUI/Session/BeamItems.cpp
+++ b/GUI/Items/BeamItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamItems.cpp
+//! @file      GUI/Items/BeamItems.cpp
 //! @brief     Implements BeamItem hierarchy
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,16 +12,16 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/BeamItems.h"
+#include "GUI/Items/BeamItems.h"
 #include "Base/Axis/IAxis.h"
 #include "Base/Const/Units.h"
 #include "Device/Beam/Beam.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
-#include "GUI/Session/FootprintItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
+#include "GUI/Items/FootprintItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/VectorItem.h"
 #include <cmath>
 
 namespace {
diff --git a/GUI/Session/BeamItems.h b/GUI/Items/BeamItems.h
similarity index 92%
rename from GUI/Session/BeamItems.h
rename to GUI/Items/BeamItems.h
index e7d4799f272b317ca4e882ef22513dd0a15ff4df..be7d5eeac7b536e0d3c5aa94f49b1fe5861613fc 100644
--- a/GUI/Session/BeamItems.h
+++ b/GUI/Items/BeamItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamItems.h
+//! @file      GUI/Items/BeamItems.h
 //! @brief     Defines BeamItem hierarchy
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_BEAMITEMS_H
-#define BORNAGAIN_GUI_SESSION_BEAMITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_BEAMITEMS_H
+#define BORNAGAIN_GUI_ITEMS_BEAMITEMS_H
 
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/SessionItem.h"
-#include "GUI/Session/SpecularBeamInclinationItem.h"
+#include "GUI/Items/SessionItem.h"
+#include "GUI/Items/SpecularBeamInclinationItem.h"
 
 class BasicAxisItem;
 class Beam;
@@ -112,4 +112,4 @@ template <typename T> T* SpecularBeamItem::setFootprintType()
     return setGroupPropertyType<T>(P_FOOTPRINT);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_BEAMITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_BEAMITEMS_H
diff --git a/GUI/Session/BeamWavelengthItem.cpp b/GUI/Items/BeamWavelengthItem.cpp
similarity index 95%
rename from GUI/Session/BeamWavelengthItem.cpp
rename to GUI/Items/BeamWavelengthItem.cpp
index f1cc6e833c87206b2cf0cdb525e24029cd9e7d1d..040ed5499edc478042cf12f0017735b95b469b91 100644
--- a/GUI/Session/BeamWavelengthItem.cpp
+++ b/GUI/Items/BeamWavelengthItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamWavelengthItem.cpp
+//! @file      GUI/Items/BeamWavelengthItem.cpp
 //! @brief     Implements class BeamWavelengthItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/BeamWavelengthItem.h"
+#include "GUI/Items/BeamWavelengthItem.h"
 
 namespace {
 const double default_wl = 0.1;
diff --git a/GUI/Session/BeamWavelengthItem.h b/GUI/Items/BeamWavelengthItem.h
similarity index 81%
rename from GUI/Session/BeamWavelengthItem.h
rename to GUI/Items/BeamWavelengthItem.h
index 98207b578999e3c0c6b050519e5ae4730755e3ee..ecfecd76f6f110413231abdeb18de679a059ec13 100644
--- a/GUI/Session/BeamWavelengthItem.h
+++ b/GUI/Items/BeamWavelengthItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/BeamWavelengthItem.h
+//! @file      GUI/Items/BeamWavelengthItem.h
 //! @brief     Defines class BeamWavelengthItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_BEAMWAVELENGTHITEM_H
-#define BORNAGAIN_GUI_SESSION_BEAMWAVELENGTHITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_BEAMWAVELENGTHITEM_H
+#define BORNAGAIN_GUI_ITEMS_BEAMWAVELENGTHITEM_H
 
-#include "GUI/Session/BeamDistributionItem.h"
+#include "GUI/Items/BeamDistributionItem.h"
 
 class BA_CORE_API_ BeamWavelengthItem : public BeamDistributionItem {
 public:
@@ -39,4 +39,4 @@ public:
     void setToRange(const RealLimits& limits);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_BEAMWAVELENGTHITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_BEAMWAVELENGTHITEM_H
diff --git a/GUI/Session/Data1DViewItem.cpp b/GUI/Items/Data1DViewItem.cpp
similarity index 97%
rename from GUI/Session/Data1DViewItem.cpp
rename to GUI/Items/Data1DViewItem.cpp
index 85cf7c75effa1248191b421cc4aca0585611e9bd..12f148fa55b300d6ffb97857508c4011d5621d38 100644
--- a/GUI/Session/Data1DViewItem.cpp
+++ b/GUI/Items/Data1DViewItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/Data1DViewItem.cpp
+//! @file      GUI/Items/Data1DViewItem.cpp
 //! @brief     Implements class Data1DViewItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/Data1DViewItem.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/Data1DViewItem.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
 #include "GUI/Models/Data/DataViewUtils.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 
 namespace {
 const QString x_axis_default_name = "X [nbins]";
diff --git a/GUI/Session/Data1DViewItem.h b/GUI/Items/Data1DViewItem.h
similarity index 93%
rename from GUI/Session/Data1DViewItem.h
rename to GUI/Items/Data1DViewItem.h
index 6a8d4c321b608b334e313a8869b72c191bd1a597..2dbde43539eafd9a725da4a55a70692ec5a62cc1 100644
--- a/GUI/Session/Data1DViewItem.h
+++ b/GUI/Items/Data1DViewItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/Data1DViewItem.h
+//! @file      GUI/Items/Data1DViewItem.h
 //! @brief     Defines class Data1DViewItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_DATA1DVIEWITEM_H
-#define BORNAGAIN_GUI_SESSION_DATA1DVIEWITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_DATA1DVIEWITEM_H
+#define BORNAGAIN_GUI_ITEMS_DATA1DVIEWITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class AmplitudeAxisItem;
 class BasicAxisItem;
@@ -105,4 +105,4 @@ private:
     JobItem* m_job_item;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_DATA1DVIEWITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_DATA1DVIEWITEM_H
diff --git a/GUI/Session/DataItem.cpp b/GUI/Items/DataItem.cpp
similarity index 97%
rename from GUI/Session/DataItem.cpp
rename to GUI/Items/DataItem.cpp
index 84a9feb73a7e26ddc1b521a1be9f2432f65c480c..8a403cbf75b1b1037e3789effb3b9fce7ddde42a 100644
--- a/GUI/Session/DataItem.cpp
+++ b/GUI/Items/DataItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DataItem.cpp
+//! @file      GUI/Items/DataItem.cpp
 //! @brief     Implements class IntensityDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "Device/Histo/IntensityDataIOFactory.h"
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/utils/Error.h"
diff --git a/GUI/Session/DataItem.h b/GUI/Items/DataItem.h
similarity index 93%
rename from GUI/Session/DataItem.h
rename to GUI/Items/DataItem.h
index 51956ba713298b708d7fe678ae84baabc9d01027..717328e539aa3f771d32f8d8e92b8811da50cd57 100644
--- a/GUI/Session/DataItem.h
+++ b/GUI/Items/DataItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DataItem.h
+//! @file      GUI/Items/DataItem.h
 //! @brief     Declares class DataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_DATAITEM_H
-#define BORNAGAIN_GUI_SESSION_DATAITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_DATAITEM_H
+#define BORNAGAIN_GUI_ITEMS_DATAITEM_H
 
 #include "Device/Data/OutputData.h"
 #include "GUI/utils/SaveLoadInterface.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <QDateTime>
 #include <mutex>
 
@@ -79,4 +79,4 @@ protected:
     std::mutex m_update_data_mutex;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_DATAITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_DATAITEM_H
diff --git a/GUI/Session/DataItemUtils.cpp b/GUI/Items/DataItemUtils.cpp
similarity index 85%
rename from GUI/Session/DataItemUtils.cpp
rename to GUI/Items/DataItemUtils.cpp
index 6cb7742fb822d747472b556f8c4c3b5edb91f5b0..5d3a4fac815ae51fc77b95855adea1e2ecec2260 100644
--- a/GUI/Session/DataItemUtils.cpp
+++ b/GUI/Items/DataItemUtils.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DataItemUtils.cpp
+//! @file      GUI/Items/DataItemUtils.cpp
 //! @brief     Implements namespace DataItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/DataItemUtils.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/DataItemUtils.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 
 namespace {
 template <class DataItemType> DataItemType* dataItem(SessionItem* parent)
diff --git a/GUI/Session/DataItemUtils.h b/GUI/Items/DataItemUtils.h
similarity index 85%
rename from GUI/Session/DataItemUtils.h
rename to GUI/Items/DataItemUtils.h
index ab041ef72de716fe1db93434d2ecbc24a3d7c662..b0892858c9f31fb8b1ff851be5f1bacf516f1071 100644
--- a/GUI/Session/DataItemUtils.h
+++ b/GUI/Items/DataItemUtils.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DataItemUtils.h
+//! @file      GUI/Items/DataItemUtils.h
 //! @brief     Defines functions in  namespace GUI::Model::DataItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_DATAITEMUTILS_H
-#define BORNAGAIN_GUI_SESSION_DATAITEMUTILS_H
+#ifndef BORNAGAIN_GUI_ITEMS_DATAITEMUTILS_H
+#define BORNAGAIN_GUI_ITEMS_DATAITEMUTILS_H
 
 class IntensityDataItem;
 class SessionItem;
@@ -31,4 +31,4 @@ SpecularDataItem* specularDataItem(SessionItem* parent);
 
 } // namespace GUI::Model::DataItemUtils
 
-#endif // BORNAGAIN_GUI_SESSION_DATAITEMUTILS_H
+#endif // BORNAGAIN_GUI_ITEMS_DATAITEMUTILS_H
diff --git a/GUI/Session/DetectorItems.cpp b/GUI/Items/DetectorItems.cpp
similarity index 95%
rename from GUI/Session/DetectorItems.cpp
rename to GUI/Items/DetectorItems.cpp
index 532966eea75d6b89ccda77cb32494cd2647305ef..23755212a290e272f58808692dfb94e5d0174b12 100644
--- a/GUI/Session/DetectorItems.cpp
+++ b/GUI/Items/DetectorItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DetectorItems.cpp
+//! @file      GUI/Items/DetectorItems.cpp
 //! @brief     Implements classes DetectorItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/DetectorItems.h"
+#include "GUI/Items/DetectorItems.h"
 #include "Device/Detector/IDetector2D.h"
 #include "Device/Mask/IShape2D.h"
 #include "Device/Resolution/ResolutionFunction2DGaussian.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ResolutionFunctionItems.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 
 namespace {
 const QString res_func_group_label = "Type";
diff --git a/GUI/Session/DetectorItems.h b/GUI/Items/DetectorItems.h
similarity index 92%
rename from GUI/Session/DetectorItems.h
rename to GUI/Items/DetectorItems.h
index 9053ab6acf1e49d61a595bd47d9cd936f71ad6e5..1de5e6df0f2bea096b164c9f89b440fc0130a69c 100644
--- a/GUI/Session/DetectorItems.h
+++ b/GUI/Items/DetectorItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DetectorItems.h
+//! @file      GUI/Items/DetectorItems.h
 //! @brief     Defines classes DetectorItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_DETECTORITEMS_H
-#define BORNAGAIN_GUI_SESSION_DETECTORITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_DETECTORITEMS_H
+#define BORNAGAIN_GUI_ITEMS_DETECTORITEMS_H
 
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class MaskContainerItem;
 class IDetector2D;
@@ -82,4 +82,4 @@ template <typename T> T* DetectorItem::setResolutionFunctionType()
     return setGroupPropertyType<T>(P_RESOLUTION_FUNCTION);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_DETECTORITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_DETECTORITEMS_H
diff --git a/GUI/Session/DistributionItems.cpp b/GUI/Items/DistributionItems.cpp
similarity index 99%
rename from GUI/Session/DistributionItems.cpp
rename to GUI/Items/DistributionItems.cpp
index 5c7b404640447b0e635d17bac251fb2f0422ea13..50a2fb4c5fe3691f0cc98baa3b857eec78c3283a 100644
--- a/GUI/Session/DistributionItems.cpp
+++ b/GUI/Items/DistributionItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DistributionItems.cpp
+//! @file      GUI/Items/DistributionItems.cpp
 //! @brief     Implements class DistributionItem and several subclasses
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/DistributionItems.h"
+#include "GUI/Items/DistributionItems.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/RealLimitsItems.h"
+#include "GUI/Items/RealLimitsItems.h"
 #include "Param/Distrib/Distributions.h"
 #include "Param/Distrib/RangedDistributions.h"
 #include <cmath>
diff --git a/GUI/Session/DistributionItems.h b/GUI/Items/DistributionItems.h
similarity index 96%
rename from GUI/Session/DistributionItems.h
rename to GUI/Items/DistributionItems.h
index fd9afa52618eb6843f4ac8c3e231bffd48fc7f2e..179ed1e38373da4decc556a7ca0e8b0c4537d8ee 100644
--- a/GUI/Session/DistributionItems.h
+++ b/GUI/Items/DistributionItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/DistributionItems.h
+//! @file      GUI/Items/DistributionItems.h
 //! @brief     Defines class DistributionItem and several subclasses
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_DISTRIBUTIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_DISTRIBUTIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_DISTRIBUTIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_DISTRIBUTIONITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IDistribution1D;
 class IRangedDistribution;
@@ -208,4 +208,4 @@ public:
     void setRightWidth(double right_width);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_DISTRIBUTIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_DISTRIBUTIONITEMS_H
diff --git a/GUI/Session/FTDecayFunctionItems.cpp b/GUI/Items/FTDecayFunctionItems.cpp
similarity index 98%
rename from GUI/Session/FTDecayFunctionItems.cpp
rename to GUI/Items/FTDecayFunctionItems.cpp
index 27d80193bb929652b76639848781e36859744b76..6e298ebc4ec7e9be922f7af2821b1e34ec979587 100644
--- a/GUI/Session/FTDecayFunctionItems.cpp
+++ b/GUI/Items/FTDecayFunctionItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FTDecayFunctionItems.cpp
+//! @file      GUI/Items/FTDecayFunctionItems.cpp
 //! @brief     Implements FTDecayFunction1DItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FTDecayFunctionItems.h"
+#include "GUI/Items/FTDecayFunctionItems.h"
 #include "Base/Const/Units.h"
 
 // --------------------------------------------------------------------------------------------- //
diff --git a/GUI/Session/FTDecayFunctionItems.h b/GUI/Items/FTDecayFunctionItems.h
similarity index 94%
rename from GUI/Session/FTDecayFunctionItems.h
rename to GUI/Items/FTDecayFunctionItems.h
index be266c3c0e9519a0e8aaf03c6d0151168b9827c3..45f9a638730c8f903fe1460a1b15002c3f6cddd9 100644
--- a/GUI/Session/FTDecayFunctionItems.h
+++ b/GUI/Items/FTDecayFunctionItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FTDecayFunctionItems.h
+//! @file      GUI/Items/FTDecayFunctionItems.h
 //! @brief     Defines FTDecayFunction1DItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FTDECAYFUNCTIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_FTDECAYFUNCTIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_FTDECAYFUNCTIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_FTDECAYFUNCTIONITEMS_H
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "Sample/Correlations/FTDecay1D.h"
 #include "Sample/Correlations/FTDecay2D.h"
 
@@ -131,4 +131,4 @@ public:
     void setEta(double eta);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_FTDECAYFUNCTIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_FTDECAYFUNCTIONITEMS_H
diff --git a/GUI/Session/FTDistributionItems.cpp b/GUI/Items/FTDistributionItems.cpp
similarity index 98%
rename from GUI/Session/FTDistributionItems.cpp
rename to GUI/Items/FTDistributionItems.cpp
index 58bde372a8e680fbbb0533909eaaa53bdd17f241..c09576c0e671754bc64435d7342a4878e78b0075 100644
--- a/GUI/Session/FTDistributionItems.cpp
+++ b/GUI/Items/FTDistributionItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FTDistributionItems.cpp
+//! @file      GUI/Items/FTDistributionItems.cpp
 //! @brief     Implements FTDistribution1DItem's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FTDistributionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
 #include "Base/Const/Units.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 
diff --git a/GUI/Session/FTDistributionItems.h b/GUI/Items/FTDistributionItems.h
similarity index 95%
rename from GUI/Session/FTDistributionItems.h
rename to GUI/Items/FTDistributionItems.h
index b0be2f8c02abe9793e27408bd0fd355c810b96c9..6d5b15c6d739287d41bfb6ab722ff5f3f10ac1af 100644
--- a/GUI/Session/FTDistributionItems.h
+++ b/GUI/Items/FTDistributionItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FTDistributionItems.h
+//! @file      GUI/Items/FTDistributionItems.h
 //! @brief     Defines FTDistribution1DItem's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FTDISTRIBUTIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_FTDISTRIBUTIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_FTDISTRIBUTIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_FTDISTRIBUTIONITEMS_H
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "Sample/Correlations/FTDistributions1D.h"
 #include "Sample/Correlations/FTDistributions2D.h"
 
@@ -162,4 +162,4 @@ public:
     void setEta(double eta);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_FTDISTRIBUTIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_FTDISTRIBUTIONITEMS_H
diff --git a/GUI/Session/FitParameterItems.cpp b/GUI/Items/FitParameterItems.cpp
similarity index 98%
rename from GUI/Session/FitParameterItems.cpp
rename to GUI/Items/FitParameterItems.cpp
index d746a2221842f61bb70b9e78b10951ed9337e7df..43301b6de02746ce73258d4a6785cfbee979c5bc 100644
--- a/GUI/Session/FitParameterItems.cpp
+++ b/GUI/Items/FitParameterItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FitParameterItems.cpp
+//! @file      GUI/Items/FitParameterItems.cpp
 //! @brief     Implements FitParameterItems family of classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,14 +12,14 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FitParameterItems.h"
+#include "GUI/Items/FitParameterItems.h"
 #include "Base/Utils/Assert.h"
 #include "Fit/Param/Parameters.h"
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include <cmath>
 
 namespace {
diff --git a/GUI/Session/FitParameterItems.h b/GUI/Items/FitParameterItems.h
similarity index 93%
rename from GUI/Session/FitParameterItems.h
rename to GUI/Items/FitParameterItems.h
index 722ade0a934f01349ec3c620e09f64b2afed4599..bf8f6e9b5782682ead537d948cefba97bf6131bd 100644
--- a/GUI/Session/FitParameterItems.h
+++ b/GUI/Items/FitParameterItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FitParameterItems.h
+//! @file      GUI/Items/FitParameterItems.h
 //! @brief     Defines classes FitParameterItem, FitParameterLinkItem, FitParameterContainerItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FITPARAMETERITEMS_H
-#define BORNAGAIN_GUI_SESSION_FITPARAMETERITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_FITPARAMETERITEMS_H
+#define BORNAGAIN_GUI_ITEMS_FITPARAMETERITEMS_H
 
 #include "Fit/Param/AttLimits.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class FitParameterLinkItem;
 
@@ -109,4 +109,4 @@ public:
     mumufit::Parameters createParameters() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_FITPARAMETERITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_FITPARAMETERITEMS_H
diff --git a/GUI/Session/FitSuiteItem.cpp b/GUI/Items/FitSuiteItem.cpp
similarity index 92%
rename from GUI/Session/FitSuiteItem.cpp
rename to GUI/Items/FitSuiteItem.cpp
index 99b9c3f01f13b978aed51eac55238343bb7c238b..f944c6fad26fbc38819c9287e52a5013119f99d8 100644
--- a/GUI/Session/FitSuiteItem.cpp
+++ b/GUI/Items/FitSuiteItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FitSuiteItem.cpp
+//! @file      GUI/Items/FitSuiteItem.cpp
 //! @brief     Implements class FitSuiteItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FitSuiteItem.h"
+#include "GUI/Items/FitSuiteItem.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/MinimizerItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/MinimizerItem.h"
+#include "GUI/Items/SessionModel.h"
 
 FitSuiteItem::FitSuiteItem() : SessionItem(M_TYPE)
 {
diff --git a/GUI/Session/FitSuiteItem.h b/GUI/Items/FitSuiteItem.h
similarity index 88%
rename from GUI/Session/FitSuiteItem.h
rename to GUI/Items/FitSuiteItem.h
index dfc25d47e7d036ccd97b0342ca0952c8314bc6ab..d5c57c935933746d11bd084bc8f5e50624ceba1f 100644
--- a/GUI/Session/FitSuiteItem.h
+++ b/GUI/Items/FitSuiteItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FitSuiteItem.h
+//! @file      GUI/Items/FitSuiteItem.h
 //! @brief     Defines class FitSuiteItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FITSUITEITEM_H
-#define BORNAGAIN_GUI_SESSION_FITSUITEITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_FITSUITEITEM_H
+#define BORNAGAIN_GUI_ITEMS_FITSUITEITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class FitParameterContainerItem;
 class MinimizerContainerItem;
@@ -51,4 +51,4 @@ public:
     void setChi2(double chi2);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_FITSUITEITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_FITSUITEITEM_H
diff --git a/GUI/Session/FootprintItems.cpp b/GUI/Items/FootprintItems.cpp
similarity index 96%
rename from GUI/Session/FootprintItems.cpp
rename to GUI/Items/FootprintItems.cpp
index e5a2d3452c20ae937c2e87c610992624a6b60836..0a606219f125bc9c81809cec216e1b4a84e84c3c 100644
--- a/GUI/Session/FootprintItems.cpp
+++ b/GUI/Items/FootprintItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FootprintItems.cpp
+//! @file      GUI/Items/FootprintItems.cpp
 //! @brief     Implements FootprintItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FootprintItems.h"
+#include "GUI/Items/FootprintItems.h"
 #include "Device/Beam/FootprintGauss.h"
 #include "Device/Beam/FootprintSquare.h"
 
diff --git a/GUI/Session/FootprintItems.h b/GUI/Items/FootprintItems.h
similarity index 89%
rename from GUI/Session/FootprintItems.h
rename to GUI/Items/FootprintItems.h
index 562c57bf11af3b91324803d7012bd9f8cf7ca3f1..d2a5f551b565fdae0213d113d609c5564522ae12 100644
--- a/GUI/Session/FootprintItems.h
+++ b/GUI/Items/FootprintItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FootprintItems.h
+//! @file      GUI/Items/FootprintItems.h
 //! @brief     Declares FootprintItem classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FOOTPRINTITEMS_H
-#define BORNAGAIN_GUI_SESSION_FOOTPRINTITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_FOOTPRINTITEMS_H
+#define BORNAGAIN_GUI_ITEMS_FOOTPRINTITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IFootprintFactor;
 
@@ -65,4 +65,4 @@ public:
     void setSquareFootprintValue(double value);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_FOOTPRINTITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_FOOTPRINTITEMS_H
diff --git a/GUI/Session/FormFactorItems.cpp b/GUI/Items/FormFactorItems.cpp
similarity index 99%
rename from GUI/Session/FormFactorItems.cpp
rename to GUI/Items/FormFactorItems.cpp
index 7fdb344d5f5bb27fd02a805437b2bd8f7087db54..d2b1ccf49972b14fd0d71063fc98780fd1604708 100644
--- a/GUI/Session/FormFactorItems.cpp
+++ b/GUI/Items/FormFactorItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FormFactorItems.cpp
+//! @file      GUI/Items/FormFactorItems.cpp
 //! @brief     Implements FormFactorItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/FormFactorItems.h"
+#include "GUI/Items/FormFactorItems.h"
 #include "Base/Const/Units.h"
 #include "GUI/Models/Group/GroupInfo.h"
 #include "Sample/HardParticle/HardParticles.h"
diff --git a/GUI/Session/FormFactorItems.h b/GUI/Items/FormFactorItems.h
similarity index 98%
rename from GUI/Session/FormFactorItems.h
rename to GUI/Items/FormFactorItems.h
index 93882c26fc5f9a2e5246dabb4f87c6031f62d576..ea0503269de0a0214fc29be6e74ca81cc5aa4a0f 100644
--- a/GUI/Session/FormFactorItems.h
+++ b/GUI/Items/FormFactorItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/FormFactorItems.h
+//! @file      GUI/Items/FormFactorItems.h
 //! @brief     Defines FormFactorItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_FORMFACTORITEMS_H
-#define BORNAGAIN_GUI_SESSION_FORMFACTORITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_FORMFACTORITEMS_H
+#define BORNAGAIN_GUI_ITEMS_FORMFACTORITEMS_H
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IFormFactor;
 class GroupInfo;
@@ -702,4 +702,4 @@ public:
 /// get a group info containing all form factors
 GroupInfo formFactorGroupInfo();
 
-#endif // BORNAGAIN_GUI_SESSION_FORMFACTORITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_FORMFACTORITEMS_H
diff --git a/GUI/Session/GroupItem.cpp b/GUI/Items/GroupItem.cpp
similarity index 97%
rename from GUI/Session/GroupItem.cpp
rename to GUI/Items/GroupItem.cpp
index 750fe7f5dc9867d4d4fa41bc5ab90efc76fd227a..c60342a941b20d4db0097acba2a60349b2e44b84 100644
--- a/GUI/Session/GroupItem.cpp
+++ b/GUI/Items/GroupItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/GroupItem.cpp
+//! @file      GUI/Items/GroupItem.cpp
 //! @brief     Implements class GroupItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/GroupItem.h"
+#include "GUI/Items/GroupItem.h"
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/utils/Error.h"
 
diff --git a/GUI/Session/GroupItem.h b/GUI/Items/GroupItem.h
similarity index 85%
rename from GUI/Session/GroupItem.h
rename to GUI/Items/GroupItem.h
index 0e8bdd205f9cba1f7173ec9375644c96eaa93222..44e4c3e6f1323bdb739eba9c6416892a6325b9ca 100644
--- a/GUI/Session/GroupItem.h
+++ b/GUI/Items/GroupItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/GroupItem.h
+//! @file      GUI/Items/GroupItem.h
 //! @brief     Defines class GroupItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_GROUPITEM_H
-#define BORNAGAIN_GUI_SESSION_GROUPITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_GROUPITEM_H
+#define BORNAGAIN_GUI_ITEMS_GROUPITEM_H
 
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/GroupItemController.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/GroupItemController.h"
+#include "GUI/Items/SessionItem.h"
 #include <memory>
 
 class GroupInfo;
@@ -58,4 +58,4 @@ template <typename T> T* GroupItem::itemOfType() const
     return dynamic_cast<T*>(m_controller->getItemOfType(T::M_TYPE));
 }
 
-#endif // BORNAGAIN_GUI_SESSION_GROUPITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_GROUPITEM_H
diff --git a/GUI/Session/GroupItemController.cpp b/GUI/Items/GroupItemController.cpp
similarity index 94%
rename from GUI/Session/GroupItemController.cpp
rename to GUI/Items/GroupItemController.cpp
index c5ea5f91c74a249b5b9079977ae16c0349460345..0b82fa39653cc15af03a58df41ac9a7604141af4 100644
--- a/GUI/Session/GroupItemController.cpp
+++ b/GUI/Items/GroupItemController.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/GroupItemController.cpp
+//! @file      GUI/Items/GroupItemController.cpp
 //! @brief     Implements class GroupItemController
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/GroupItemController.h"
+#include "GUI/Items/GroupItemController.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/ItemFactory.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/ItemFactory.h"
+#include "GUI/Items/SessionItem.h"
 
 GroupItemController::GroupItemController(SessionItem* groupItem, GroupInfo groupInfo)
     : m_groupItem(groupItem), m_groupInfo(groupInfo)
diff --git a/GUI/Session/GroupItemController.h b/GUI/Items/GroupItemController.h
similarity index 87%
rename from GUI/Session/GroupItemController.h
rename to GUI/Items/GroupItemController.h
index 1b2fb19040d2ad997f98e2155bc7eeeb8474b340..b59e7995309efe3c8ee4836b1aaf6e1cf3ed57ac 100644
--- a/GUI/Session/GroupItemController.h
+++ b/GUI/Items/GroupItemController.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/GroupItemController.h
+//! @file      GUI/Items/GroupItemController.h
 //! @brief     Defines class GroupItemController
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_GROUPITEMCONTROLLER_H
-#define BORNAGAIN_GUI_SESSION_GROUPITEMCONTROLLER_H
+#ifndef BORNAGAIN_GUI_ITEMS_GROUPITEMCONTROLLER_H
+#define BORNAGAIN_GUI_ITEMS_GROUPITEMCONTROLLER_H
 
 #include "GUI/Models/Group/GroupInfo.h"
 #include <QStringList>
@@ -52,4 +52,4 @@ private:
     GroupInfo m_groupInfo;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_GROUPITEMCONTROLLER_H
+#endif // BORNAGAIN_GUI_ITEMS_GROUPITEMCONTROLLER_H
diff --git a/GUI/Session/InstrumentItems.cpp b/GUI/Items/InstrumentItems.cpp
similarity index 96%
rename from GUI/Session/InstrumentItems.cpp
rename to GUI/Items/InstrumentItems.cpp
index 552dadb0a5618b68655a78301a72640a78c177b7..515c255c1b6e42f0409988717f9a46764f96d02e 100644
--- a/GUI/Session/InstrumentItems.cpp
+++ b/GUI/Items/InstrumentItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/InstrumentItems.cpp
+//! @file      GUI/Items/InstrumentItems.cpp
 //! @brief     Implement class InstrumentItem and all its children
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "Base/Const/Units.h"
 #include "Base/Pixel/RectangularPixel.h"
 #include "Core/Simulation/DepthProbeSimulation.h"
@@ -21,19 +21,19 @@
 #include "Device/Coord/CoordSystem2D.h"
 #include "Device/Detector/RectangularDetector.h"
 #include "Device/Detector/SphericalDetector.h"
-#include "GUI/Session/BackgroundItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
-#include "GUI/Session/DetectorItems.h"
+#include "GUI/Items/BackgroundItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
+#include "GUI/Items/DetectorItems.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/utils/Helpers.h"
 
 namespace {
diff --git a/GUI/Session/InstrumentItems.h b/GUI/Items/InstrumentItems.h
similarity index 95%
rename from GUI/Session/InstrumentItems.h
rename to GUI/Items/InstrumentItems.h
index 30cbcf506df1bd2afd8b9ad86224ff761542d63f..226cd3a4555e421bad4761cf189ea38fa5fddcfa 100644
--- a/GUI/Session/InstrumentItems.h
+++ b/GUI/Items/InstrumentItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/InstrumentItems.h
+//! @file      GUI/Items/InstrumentItems.h
 //! @brief     Defines class InstrumentItem and all its children
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_INSTRUMENTITEMS_H
-#define BORNAGAIN_GUI_SESSION_INSTRUMENTITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_INSTRUMENTITEMS_H
+#define BORNAGAIN_GUI_ITEMS_INSTRUMENTITEMS_H
 
-#include "GUI/Session/BeamItems.h" // inheritance prevents forward declaration
+#include "GUI/Items/BeamItems.h" // inheritance prevents forward declaration
 
 class BackgroundItem;
 class DataItem;
@@ -210,4 +210,4 @@ template <typename T> T* Instrument2DItem::setDetectorType()
     return setGroupPropertyType<T>(P_DETECTOR);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_INSTRUMENTITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_INSTRUMENTITEMS_H
diff --git a/GUI/Session/IntensityDataItem.cpp b/GUI/Items/IntensityDataItem.cpp
similarity index 97%
rename from GUI/Session/IntensityDataItem.cpp
rename to GUI/Items/IntensityDataItem.cpp
index 34de6d77557b030cf12a35ed2ff9ec6357dabc25..532c739f50c6c0088b47d11828f178890b66cfed 100644
--- a/GUI/Session/IntensityDataItem.cpp
+++ b/GUI/Items/IntensityDataItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/IntensityDataItem.cpp
+//! @file      GUI/Items/IntensityDataItem.cpp
 //! @brief     Implements class IntensityDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Data/ImportDataInfo.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Models/Data/MaskUnitsConverter.h"
-#include "GUI/Session/ProjectionItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/ProjectionItems.h"
+#include "GUI/Items/SessionModel.h"
 
 namespace {
 ComboProperty gradientCombo()
diff --git a/GUI/Session/IntensityDataItem.h b/GUI/Items/IntensityDataItem.h
similarity index 94%
rename from GUI/Session/IntensityDataItem.h
rename to GUI/Items/IntensityDataItem.h
index 1c0fd2b57871c535bcedb4252a97510ba113006c..9ac029309ca6b0916017213be2934fe1ab0ea48c 100644
--- a/GUI/Session/IntensityDataItem.h
+++ b/GUI/Items/IntensityDataItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/IntensityDataItem.h
+//! @file      GUI/Items/IntensityDataItem.h
 //! @brief     Defines class IntensityDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_INTENSITYDATAITEM_H
-#define BORNAGAIN_GUI_SESSION_INTENSITYDATAITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_INTENSITYDATAITEM_H
+#define BORNAGAIN_GUI_ITEMS_INTENSITYDATAITEM_H
 
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 
 class BasicAxisItem;
 class AmplitudeAxisItem;
@@ -135,4 +135,4 @@ private:
     void updateAxesLabels();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_INTENSITYDATAITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_INTENSITYDATAITEM_H
diff --git a/GUI/Session/InterferenceItems.cpp b/GUI/Items/InterferenceItems.cpp
similarity index 98%
rename from GUI/Session/InterferenceItems.cpp
rename to GUI/Items/InterferenceItems.cpp
index 2f3ba9aa72a97deff6ffbc7bcaa690be9d6b7a26..33778e05c345353551b44e6e2d76d53ebcae4b5b 100644
--- a/GUI/Session/InterferenceItems.cpp
+++ b/GUI/Items/InterferenceItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/InterferenceItems.cpp
+//! @file      GUI/Items/InterferenceItems.cpp
 //! @brief     Implements InterferenceItems's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,14 +12,14 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/InterferenceItems.h"
+#include "GUI/Items/InterferenceItems.h"
 #include "Base/Const/Units.h"
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/FTDecayFunctionItems.h"
-#include "GUI/Session/FTDistributionItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/Lattice2DItems.h"
+#include "GUI/Items/FTDecayFunctionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/Lattice2DItems.h"
 #include "Sample/Aggregate/Interferences.h"
 
 // TODO (when back compatibility will be broken  again)
diff --git a/GUI/Session/InterferenceItems.h b/GUI/Items/InterferenceItems.h
similarity index 96%
rename from GUI/Session/InterferenceItems.h
rename to GUI/Items/InterferenceItems.h
index 6e9ca5fc77082542c3f7c100ab1f40bd7e706a44..95593237d7a2de53ab32f54e61d33a9a486997ff 100644
--- a/GUI/Session/InterferenceItems.h
+++ b/GUI/Items/InterferenceItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/InterferenceItems.h
+//! @file      GUI/Items/InterferenceItems.h
 //! @brief     Defines InterferenceItems's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_INTERFERENCEITEMS_H
-#define BORNAGAIN_GUI_SESSION_INTERFERENCEITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_INTERFERENCEITEMS_H
+#define BORNAGAIN_GUI_ITEMS_INTERFERENCEITEMS_H
 
 #include "GUI/Models/Group/SelectionDescriptor.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 class FTDecayFunction1DItem;
 class FTDecayFunction2DItem;
@@ -221,4 +221,4 @@ template <typename T> T* InterferenceRadialParaCrystalItem::setPDFType()
     return setGroupPropertyType<T>(P_PDF);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_INTERFERENCEITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_INTERFERENCEITEMS_H
diff --git a/GUI/Session/ItemCatalog.cpp b/GUI/Items/ItemCatalog.cpp
similarity index 89%
rename from GUI/Session/ItemCatalog.cpp
rename to GUI/Items/ItemCatalog.cpp
index ccd617a26930e3c46f374e8934c8b1a380da335c..277615775c56b4b77c8fcec469f0e5b20cf52736 100644
--- a/GUI/Session/ItemCatalog.cpp
+++ b/GUI/Items/ItemCatalog.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemCatalog.cpp
+//! @file      GUI/Items/ItemCatalog.cpp
 //! @brief     Implements class ItemCatalog
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,55 +12,55 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ItemCatalog.h"
+#include "GUI/Items/ItemCatalog.h"
 #include "Base/Utils/Assert.h"
-#include "GUI/Session/BackgroundItems.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
-#include "GUI/Session/Data1DViewItem.h"
+#include "GUI/Items/BackgroundItems.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
+#include "GUI/Items/Data1DViewItem.h"
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FTDecayFunctionItems.h"
-#include "GUI/Session/FTDistributionItems.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/FootprintItems.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/Lattice2DItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/MaterialDataItems.h"
-#include "GUI/Session/MaterialItem.h"
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MinimizerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParameterTreeItems.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/ProjectionItems.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/RealLimitsItems.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/ResolutionFunctionItems.h"
-#include "GUI/Session/RotationItems.h"
-#include "GUI/Session/SimulationOptionsItem.h"
-#include "GUI/Session/SpecularBeamInclinationItem.h"
-#include "GUI/Session/SpecularDataItem.h"
-#include "GUI/Session/SphericalDetectorItem.h"
-#include "GUI/Session/TransformationItem.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/FTDecayFunctionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/FootprintItems.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/Lattice2DItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/MaterialDataItems.h"
+#include "GUI/Items/MaterialItem.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MinimizerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParameterTreeItems.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/ProjectionItems.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/RealLimitsItems.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
+#include "GUI/Items/RotationItems.h"
+#include "GUI/Items/SimulationOptionsItem.h"
+#include "GUI/Items/SpecularBeamInclinationItem.h"
+#include "GUI/Items/SpecularDataItem.h"
+#include "GUI/Items/SphericalDetectorItem.h"
+#include "GUI/Items/TransformationItem.h"
+#include "GUI/Items/VectorItem.h"
 
 ItemCatalog::ItemCatalog()
 {
diff --git a/GUI/Session/ItemCatalog.h b/GUI/Items/ItemCatalog.h
similarity index 91%
rename from GUI/Session/ItemCatalog.h
rename to GUI/Items/ItemCatalog.h
index 47aca58258283bc96185adf81c1499c87d22cf77..8f298e9621de9b1ba755bd482098782ba49a30cd 100644
--- a/GUI/Session/ItemCatalog.h
+++ b/GUI/Items/ItemCatalog.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemCatalog.h
+//! @file      GUI/Items/ItemCatalog.h
 //! @brief     Defines class ItemCatalog
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMCATALOG_H
-#define BORNAGAIN_GUI_SESSION_ITEMCATALOG_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMCATALOG_H
+#define BORNAGAIN_GUI_ITEMS_ITEMCATALOG_H
 
 #include "Base/Utils/IFactory.h"
 #include <QMap>
@@ -64,4 +64,4 @@ private:
 };
 
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMCATALOG_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMCATALOG_H
diff --git a/GUI/Session/ItemFactory.cpp b/GUI/Items/ItemFactory.cpp
similarity index 85%
rename from GUI/Session/ItemFactory.cpp
rename to GUI/Items/ItemFactory.cpp
index 0281ddd92082d0c7941a946c17909a79b7289934..4a199a24f49dabe931c1dc18797cde50481e587a 100644
--- a/GUI/Session/ItemFactory.cpp
+++ b/GUI/Items/ItemFactory.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemFactory.cpp
+//! @file      GUI/Items/ItemFactory.cpp
 //! @brief     Implements class ItemFactory
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ItemFactory.h"
-#include "GUI/Session/ItemCatalog.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/ItemFactory.h"
+#include "GUI/Items/ItemCatalog.h"
+#include "GUI/Items/SessionItem.h"
 
 SessionItem* GUI::Model::ItemFactory::CreateItem(const QString& model_name, SessionItem* parent)
 {
diff --git a/GUI/Session/ItemFactory.h b/GUI/Items/ItemFactory.h
similarity index 87%
rename from GUI/Session/ItemFactory.h
rename to GUI/Items/ItemFactory.h
index e63f09c4c06ba8d3c37f4aa42c1072fc1e66cd3a..fbc25384fcdbeb3d3edf2141d2cfc4171d6c0017 100644
--- a/GUI/Session/ItemFactory.h
+++ b/GUI/Items/ItemFactory.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemFactory.h
+//! @file      GUI/Items/ItemFactory.h
 //! @brief     Defines namespace GUI::Model::ItemFactory
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMFACTORY_H
-#define BORNAGAIN_GUI_SESSION_ITEMFACTORY_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMFACTORY_H
+#define BORNAGAIN_GUI_ITEMS_ITEMFACTORY_H
 
 #include <QString>
 
@@ -39,4 +39,4 @@ template <typename ItemType> ItemType* CreateItem(SessionItem* parent)
 
 }; // namespace GUI::Model::ItemFactory
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMFACTORY_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMFACTORY_H
diff --git a/GUI/Session/ItemFileNameUtils.cpp b/GUI/Items/ItemFileNameUtils.cpp
similarity index 93%
rename from GUI/Session/ItemFileNameUtils.cpp
rename to GUI/Items/ItemFileNameUtils.cpp
index d5b6290e4c023a222c315004e1eee13cd9170d65..19fdffe7c2ba2237b0426ae3b3cd33be608a6e50 100644
--- a/GUI/Session/ItemFileNameUtils.cpp
+++ b/GUI/Items/ItemFileNameUtils.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemFileNameUtils.cpp
+//! @file      GUI/Items/ItemFileNameUtils.cpp
 //! @brief     Defines auxiliary functions in ItemFileNameUtils namespace.
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/utils/Helpers.h"
 
 namespace {
diff --git a/GUI/Session/ItemFileNameUtils.h b/GUI/Items/ItemFileNameUtils.h
similarity index 85%
rename from GUI/Session/ItemFileNameUtils.h
rename to GUI/Items/ItemFileNameUtils.h
index d7953d8cf663f5b55fe9950e7864e59870955bb4..a97ec19acc9b232866a3fc26e427bb3f01049513 100644
--- a/GUI/Session/ItemFileNameUtils.h
+++ b/GUI/Items/ItemFileNameUtils.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemFileNameUtils.h
+//! @file      GUI/Items/ItemFileNameUtils.h
 //! @brief     Defines namespace GUI::Model::FilenameUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMFILENAMEUTILS_H
-#define BORNAGAIN_GUI_SESSION_ITEMFILENAMEUTILS_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMFILENAMEUTILS_H
+#define BORNAGAIN_GUI_ITEMS_ITEMFILENAMEUTILS_H
 
 #include <QString>
 
@@ -41,4 +41,4 @@ QStringList nonXMLFileNameFilters();
 
 } // namespace GUI::Model::FilenameUtils
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMFILENAMEUTILS_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMFILENAMEUTILS_H
diff --git a/GUI/Session/ItemWithDistribution.h b/GUI/Items/ItemWithDistribution.h
similarity index 81%
rename from GUI/Session/ItemWithDistribution.h
rename to GUI/Items/ItemWithDistribution.h
index 7786f2e791d3654c6067eb893276aef212283e4d..869b6ceeb490766b956f4a616cebe7c41e12cd06 100644
--- a/GUI/Session/ItemWithDistribution.h
+++ b/GUI/Items/ItemWithDistribution.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemWithDistribution.h
+//! @file      GUI/Items/ItemWithDistribution.h
 //! @brief     Defines abstract item with a distribution
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMWITHDISTRIBUTION_H
-#define BORNAGAIN_GUI_SESSION_ITEMWITHDISTRIBUTION_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMWITHDISTRIBUTION_H
+#define BORNAGAIN_GUI_ITEMS_ITEMWITHDISTRIBUTION_H
 
 #include "Wrap/WinDllMacros.h"
 
@@ -33,4 +33,4 @@ public:
     virtual ~ItemWithDistribution() = default;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMWITHDISTRIBUTION_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMWITHDISTRIBUTION_H
diff --git a/GUI/Session/ItemWithMaterial.cpp b/GUI/Items/ItemWithMaterial.cpp
similarity index 89%
rename from GUI/Session/ItemWithMaterial.cpp
rename to GUI/Items/ItemWithMaterial.cpp
index 3c9f97dfdad2cb51601685704841a10cf1b8506c..0598d7235b5a0f401d03b9328dc08ec7e31fb574 100644
--- a/GUI/Session/ItemWithMaterial.cpp
+++ b/GUI/Items/ItemWithMaterial.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemWithMaterial.cpp
+//! @file      GUI/Items/ItemWithMaterial.cpp
 //! @brief     Implements class ItemWithMaterial
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobModelFunctions.h"
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobModelFunctions.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/MaterialItemUtils.h"
 
 void ItemWithMaterial::setMaterial(const MaterialItem* materialItem)
 {
diff --git a/GUI/Session/ItemWithMaterial.h b/GUI/Items/ItemWithMaterial.h
similarity index 84%
rename from GUI/Session/ItemWithMaterial.h
rename to GUI/Items/ItemWithMaterial.h
index 832e6593d38c7ff7cd3e3695d2ce1d6e17410d10..12206cc7747650e7ccd0b29220f1d2004929e895 100644
--- a/GUI/Session/ItemWithMaterial.h
+++ b/GUI/Items/ItemWithMaterial.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemWithMaterial.h
+//! @file      GUI/Items/ItemWithMaterial.h
 //! @brief     Defines abstract item with a material property
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMWITHMATERIAL_H
-#define BORNAGAIN_GUI_SESSION_ITEMWITHMATERIAL_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMWITHMATERIAL_H
+#define BORNAGAIN_GUI_ITEMS_ITEMWITHMATERIAL_H
 
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 class MaterialItem;
 
@@ -45,4 +45,4 @@ protected:
     ItemWithMaterial(const QString& model_type);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMWITHMATERIAL_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMWITHMATERIAL_H
diff --git a/GUI/Session/ItemWithParticles.cpp b/GUI/Items/ItemWithParticles.cpp
similarity index 94%
rename from GUI/Session/ItemWithParticles.cpp
rename to GUI/Items/ItemWithParticles.cpp
index cb445d572fd5e13973488e31caf52b4e1e8b8ca9..a2286cf51b0b085068594756df75071314d9ffb5 100644
--- a/GUI/Session/ItemWithParticles.cpp
+++ b/GUI/Items/ItemWithParticles.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemWithParticles.cpp
+//! @file      GUI/Items/ItemWithParticles.cpp
 //! @brief     Implements class ItemWithParticles
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,14 +12,14 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ItemWithParticles.h"
+#include "GUI/Items/ItemWithParticles.h"
 #include "Base/Vector/Transform3D.h"
-#include "GUI/Session/RotationItems.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/TransformationItem.h"
+#include "GUI/Items/RotationItems.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/TransformationItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 DoubleDescriptor ItemWithParticles::abundance() const
 {
diff --git a/GUI/Session/ItemWithParticles.h b/GUI/Items/ItemWithParticles.h
similarity index 89%
rename from GUI/Session/ItemWithParticles.h
rename to GUI/Items/ItemWithParticles.h
index 9c52ea11bcc3ac2b0e94c277c21b92c9b1965747..b7db1fca525cd46f87f204b520be7d291eb7ddb7 100644
--- a/GUI/Session/ItemWithParticles.h
+++ b/GUI/Items/ItemWithParticles.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ItemWithParticles.h
+//! @file      GUI/Items/ItemWithParticles.h
 //! @brief     Defines abstract item with a material property
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ITEMWITHPARTICLES_H
-#define BORNAGAIN_GUI_SESSION_ITEMWITHPARTICLES_H
+#ifndef BORNAGAIN_GUI_ITEMS_ITEMWITHPARTICLES_H
+#define BORNAGAIN_GUI_ITEMS_ITEMWITHPARTICLES_H
 
 #include "Base/Vector/Vectors3D.h"
 #include "GUI/Models/Group/SelectionDescriptor.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 class RotationItem;
 class TransformationItem;
@@ -66,4 +66,4 @@ private:
     RotationItem* rotationItem() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_ITEMWITHPARTICLES_H
+#endif // BORNAGAIN_GUI_ITEMS_ITEMWITHPARTICLES_H
diff --git a/GUI/Session/JobItem.cpp b/GUI/Items/JobItem.cpp
similarity index 94%
rename from GUI/Session/JobItem.cpp
rename to GUI/Items/JobItem.cpp
index e0ef4c72801016886354d3ddb526eae8e37d68a0..d6c60d67b64332c005891cf54c3bb99a4dd54c5a 100644
--- a/GUI/Session/JobItem.cpp
+++ b/GUI/Items/JobItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobItem.cpp
+//! @file      GUI/Items/JobItem.cpp
 //! @brief     Implements class JobItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,21 +12,21 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "Base/Utils/Assert.h"
-#include "GUI/Session/Data1DViewItem.h"
+#include "GUI/Items/Data1DViewItem.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParameterTreeItems.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SimulationOptionsItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParameterTreeItems.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 
 JobItem::JobItem() : SessionItem(M_TYPE)
 {
diff --git a/GUI/Session/JobItem.h b/GUI/Items/JobItem.h
similarity index 95%
rename from GUI/Session/JobItem.h
rename to GUI/Items/JobItem.h
index a29716b46607c39607811d56f811c42b975a2744..ff41e4b940be98b4cba048d4892afe5d2465d867 100644
--- a/GUI/Session/JobItem.h
+++ b/GUI/Items/JobItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobItem.h
+//! @file      GUI/Items/JobItem.h
 //! @brief     Defines class JobItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_JOBITEM_H
-#define BORNAGAIN_GUI_SESSION_JOBITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_JOBITEM_H
+#define BORNAGAIN_GUI_ITEMS_JOBITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/Models/Job/JobStatus.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 class DataItem;
 class Data1DViewItem;
@@ -159,4 +159,4 @@ template <typename T> T* JobItem::setDataType()
     return model()->insertItem<T>(this, -1, T_OUTPUT);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_JOBITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_JOBITEM_H
diff --git a/GUI/Session/JobItemUtils.cpp b/GUI/Items/JobItemUtils.cpp
similarity index 97%
rename from GUI/Session/JobItemUtils.cpp
rename to GUI/Items/JobItemUtils.cpp
index bd55f5b75c93065df507a7e064e01a628f60488c..167ed44430e5d5c7a5a12e117a328cb10c03d38b 100644
--- a/GUI/Session/JobItemUtils.cpp
+++ b/GUI/Items/JobItemUtils.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobItemUtils.cpp
+//! @file      GUI/Items/JobItemUtils.cpp
 //! @brief     Implements class JobItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/JobItemUtils.h"
+#include "GUI/Items/JobItemUtils.h"
 #include "Core/Simulation/ISimulation.h"
 #include "Device/Coord/ICoordSystem.h"
 #include "Device/Histo/SimulationResult.h"
-#include "GUI/Session/DataItem.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/DataItem.h"
+#include "GUI/Items/InstrumentItems.h"
 
 namespace {
 
diff --git a/GUI/Session/JobItemUtils.h b/GUI/Items/JobItemUtils.h
similarity index 91%
rename from GUI/Session/JobItemUtils.h
rename to GUI/Items/JobItemUtils.h
index 98cdc1bdf9e7c73cec550ca1f82fdbd1ac18e82d..3d0780c8c576e87c885d28cccb219e4615bab155 100644
--- a/GUI/Session/JobItemUtils.h
+++ b/GUI/Items/JobItemUtils.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobItemUtils.h
+//! @file      GUI/Items/JobItemUtils.h
 //! @brief     Defines namespace GUI::Model::JobItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_JOBITEMUTILS_H
-#define BORNAGAIN_GUI_SESSION_JOBITEMUTILS_H
+#ifndef BORNAGAIN_GUI_ITEMS_JOBITEMUTILS_H
+#define BORNAGAIN_GUI_ITEMS_JOBITEMUTILS_H
 
 #include "Device/Detector/IDetector.h"
 #include "GUI/Models/Group/ComboProperty.h"
@@ -53,4 +53,4 @@ ComboProperty availableUnits(const ICoordSystem& converter);
 
 } // namespace GUI::Model::JobItemUtils
 
-#endif // BORNAGAIN_GUI_SESSION_JOBITEMUTILS_H
+#endif // BORNAGAIN_GUI_ITEMS_JOBITEMUTILS_H
diff --git a/GUI/Session/JobModelFunctions.cpp b/GUI/Items/JobModelFunctions.cpp
similarity index 92%
rename from GUI/Session/JobModelFunctions.cpp
rename to GUI/Items/JobModelFunctions.cpp
index 45755017e239e9276e97d1acd92ae8c10dbef545..16f30ef087d7df2518e2bc24f6a4c8e0d30d6438 100644
--- a/GUI/Session/JobModelFunctions.cpp
+++ b/GUI/Items/JobModelFunctions.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobModelFunctions.cpp
+//! @file      GUI/Items/JobModelFunctions.cpp
 //! @brief     Implements auxiliary functions in JobModelFunctions namespace.
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,28 +12,28 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/JobModelFunctions.h"
+#include "GUI/Items/JobModelFunctions.h"
 #include "Base/Utils/Assert.h"
 #include "Device/Instrument/Instrument.h"
-#include "GUI/Session/Data1DViewItem.h"
+#include "GUI/Items/Data1DViewItem.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/MaterialItemUtils.h"
-#include "GUI/Session/MinimizerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/MaterialItemUtils.h"
+#include "GUI/Items/MinimizerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/utils/Helpers.h"
 #include <map>
 
diff --git a/GUI/Session/JobModelFunctions.h b/GUI/Items/JobModelFunctions.h
similarity index 89%
rename from GUI/Session/JobModelFunctions.h
rename to GUI/Items/JobModelFunctions.h
index 4d445b2765480a770cb5639fd5cd28fae75c38fb..3f33c782e350decb09c42c972d056bf7763f04f8 100644
--- a/GUI/Session/JobModelFunctions.h
+++ b/GUI/Items/JobModelFunctions.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/JobModelFunctions.h
+//! @file      GUI/Items/JobModelFunctions.h
 //! @brief     Defines auxiliary functions in namespace GUI::Model::JobModelFunctions.
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_JOBMODELFUNCTIONS_H
-#define BORNAGAIN_GUI_SESSION_JOBMODELFUNCTIONS_H
+#ifndef BORNAGAIN_GUI_ITEMS_JOBMODELFUNCTIONS_H
+#define BORNAGAIN_GUI_ITEMS_JOBMODELFUNCTIONS_H
 
 class InstrumentItem;
 class JobItem;
@@ -51,4 +51,4 @@ const JobItem* findJobItem(const SessionItem* item);
 
 } // namespace GUI::Model::JobFunctions
 
-#endif // BORNAGAIN_GUI_SESSION_JOBMODELFUNCTIONS_H
+#endif // BORNAGAIN_GUI_ITEMS_JOBMODELFUNCTIONS_H
diff --git a/GUI/Session/Lattice2DItems.cpp b/GUI/Items/Lattice2DItems.cpp
similarity index 98%
rename from GUI/Session/Lattice2DItems.cpp
rename to GUI/Items/Lattice2DItems.cpp
index 440566f05abd3a27606758ff9c3ec83a56f5ce32..63df18e67b7c16ecc4d2d2e0cad99db6c9195351 100644
--- a/GUI/Session/Lattice2DItems.cpp
+++ b/GUI/Items/Lattice2DItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/Lattice2DItems.cpp
+//! @file      GUI/Items/Lattice2DItems.cpp
 //! @brief     Implements classes Lattice2DItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/Lattice2DItems.h"
+#include "GUI/Items/Lattice2DItems.h"
 #include "Base/Const/Units.h"
 #include "Sample/Lattice/Lattice2D.h"
 
diff --git a/GUI/Session/Lattice2DItems.h b/GUI/Items/Lattice2DItems.h
similarity index 90%
rename from GUI/Session/Lattice2DItems.h
rename to GUI/Items/Lattice2DItems.h
index 7a27b2b75886f896c632316cbcaefd0ac0c9efa0..392320f130d8d082f202608a0fa0c3dac65cb720 100644
--- a/GUI/Session/Lattice2DItems.h
+++ b/GUI/Items/Lattice2DItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/Lattice2DItems.h
+//! @file      GUI/Items/Lattice2DItems.h
 //! @brief     Defines classes Lattice2DItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_LATTICE2DITEMS_H
-#define BORNAGAIN_GUI_SESSION_LATTICE2DITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_LATTICE2DITEMS_H
+#define BORNAGAIN_GUI_ITEMS_LATTICE2DITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 class Lattice2D;
 
 class Lattice2DItem : public SessionItem {
@@ -82,4 +82,4 @@ public:
     void setLatticeLength(double length);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_LATTICE2DITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_LATTICE2DITEMS_H
diff --git a/GUI/Session/LayerItem.cpp b/GUI/Items/LayerItem.cpp
similarity index 94%
rename from GUI/Session/LayerItem.cpp
rename to GUI/Items/LayerItem.cpp
index f2fc64462ba1cd3ed5382d9beba9da33e608b14d..a737cbcb66e4cc5d0ca4bd34db499c41b3c1752a 100644
--- a/GUI/Session/LayerItem.cpp
+++ b/GUI/Items/LayerItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/LayerItem.cpp
+//! @file      GUI/Items/LayerItem.cpp
 //! @brief     Implements class LayerItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,13 +12,13 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/LayerItem.h"
+#include "GUI/Items/LayerItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MaterialItemUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MaterialItemUtils.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Group/SelectionDescriptor.h"
 #include "GUI/Models/Types/UIntDescriptor.h"
 
diff --git a/GUI/Session/LayerItem.h b/GUI/Items/LayerItem.h
similarity index 92%
rename from GUI/Session/LayerItem.h
rename to GUI/Items/LayerItem.h
index 4a870f643645e9610662555e24631cb8067784d2..17a602709165666fd4280e7feaa564d3cd12a078 100644
--- a/GUI/Session/LayerItem.h
+++ b/GUI/Items/LayerItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/LayerItem.h
+//! @file      GUI/Items/LayerItem.h
 //! @brief     Defines class LayerItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_LAYERITEM_H
-#define BORNAGAIN_GUI_SESSION_LAYERITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_LAYERITEM_H
+#define BORNAGAIN_GUI_ITEMS_LAYERITEM_H
 
-#include "GUI/Session/ItemWithMaterial.h"
+#include "GUI/Items/ItemWithMaterial.h"
 #include "GUI/Models/Group/SelectionDescriptor.h"
 #include <variant>
 
@@ -78,4 +78,4 @@ template <typename T> T* LayerItem::setRoughnessType()
     return setGroupPropertyType<T>(P_ROUGHNESS);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_LAYERITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_LAYERITEM_H
diff --git a/GUI/Session/LayerRoughnessItems.cpp b/GUI/Items/LayerRoughnessItems.cpp
similarity index 95%
rename from GUI/Session/LayerRoughnessItems.cpp
rename to GUI/Items/LayerRoughnessItems.cpp
index 529cbc8d2167284e6e1ad4b615d951c119d30ad2..3cbed6ce710e703d72a04909a39ca6e2b3534a79 100644
--- a/GUI/Session/LayerRoughnessItems.cpp
+++ b/GUI/Items/LayerRoughnessItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/LayerRoughnessItems.cpp
+//! @file      GUI/Items/LayerRoughnessItems.cpp
 //! @brief     Implements classes LayerRoughnessItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/LayerRoughnessItems.h"
+#include "GUI/Items/LayerRoughnessItems.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 
 namespace {
diff --git a/GUI/Session/LayerRoughnessItems.h b/GUI/Items/LayerRoughnessItems.h
similarity index 83%
rename from GUI/Session/LayerRoughnessItems.h
rename to GUI/Items/LayerRoughnessItems.h
index 48db277022f0afce630cfab8bab693444da062f9..fe8db0bd8777aee396383b32589b1b53616591a0 100644
--- a/GUI/Session/LayerRoughnessItems.h
+++ b/GUI/Items/LayerRoughnessItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/LayerRoughnessItems.h
+//! @file      GUI/Items/LayerRoughnessItems.h
 //! @brief     Defines classes LayerRoughnessItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_LAYERROUGHNESSITEMS_H
-#define BORNAGAIN_GUI_SESSION_LAYERROUGHNESSITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_LAYERROUGHNESSITEMS_H
+#define BORNAGAIN_GUI_ITEMS_LAYERROUGHNESSITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class DoubleDescriptor;
 
@@ -42,4 +42,4 @@ public:
     DoubleDescriptor lateralCorrelationLength() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_LAYERROUGHNESSITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_LAYERROUGHNESSITEMS_H
diff --git a/GUI/Session/MaskItems.cpp b/GUI/Items/MaskItems.cpp
similarity index 99%
rename from GUI/Session/MaskItems.cpp
rename to GUI/Items/MaskItems.cpp
index 25f3bb05f948d5a1ae8b8ccb84e1f7661846bfcd..f0dcf0e72110047be19b07d5e3631f595f68271f 100644
--- a/GUI/Session/MaskItems.cpp
+++ b/GUI/Items/MaskItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaskItems.cpp
+//! @file      GUI/Items/MaskItems.cpp
 //! @brief     Implements MaskItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "Device/Mask/Ellipse.h"
 #include "Device/Mask/InfinitePlane.h"
 #include "Device/Mask/Line.h"
diff --git a/GUI/Session/MaskItems.h b/GUI/Items/MaskItems.h
similarity index 96%
rename from GUI/Session/MaskItems.h
rename to GUI/Items/MaskItems.h
index 6eee070bf3a4136adf537c1e872ccae42ac85604..f0a65fec68df0c8aebb670ca01c77bca94c1a5c9 100644
--- a/GUI/Session/MaskItems.h
+++ b/GUI/Items/MaskItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaskItems.h
+//! @file      GUI/Items/MaskItems.h
 //! @brief     Defines MaskItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MASKITEMS_H
-#define BORNAGAIN_GUI_SESSION_MASKITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_MASKITEMS_H
+#define BORNAGAIN_GUI_ITEMS_MASKITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IShape2D;
 
@@ -188,4 +188,4 @@ public:
     virtual std::unique_ptr<IShape2D> createShape(double scale) const override;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MASKITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_MASKITEMS_H
diff --git a/GUI/Session/MaterialDataItems.cpp b/GUI/Items/MaterialDataItems.cpp
similarity index 95%
rename from GUI/Session/MaterialDataItems.cpp
rename to GUI/Items/MaterialDataItems.cpp
index 6aae15fe8240ab04470780100e17cc559c7a74a2..c57a8b9664e22b1415bd3f88573123305fb9c36a 100644
--- a/GUI/Session/MaterialDataItems.cpp
+++ b/GUI/Items/MaterialDataItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialDataItems.cpp
+//! @file      GUI/Items/MaterialDataItems.cpp
 //! @brief     Implements MaterialDataItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MaterialDataItems.h"
+#include "GUI/Items/MaterialDataItems.h"
 
 MaterialDataItem::MaterialDataItem(const QString& modelType) : SessionItem(modelType)
 {
diff --git a/GUI/Session/MaterialDataItems.h b/GUI/Items/MaterialDataItems.h
similarity index 84%
rename from GUI/Session/MaterialDataItems.h
rename to GUI/Items/MaterialDataItems.h
index 59463520aa693230a8068ee40b43b38579d65f09..f8cc85addd6301223265c81815415160b9146547 100644
--- a/GUI/Session/MaterialDataItems.h
+++ b/GUI/Items/MaterialDataItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialDataItems.h
+//! @file      GUI/Items/MaterialDataItems.h
 //! @brief     Defines MaterialDataItems classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MATERIALDATAITEMS_H
-#define BORNAGAIN_GUI_SESSION_MATERIALDATAITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_MATERIALDATAITEMS_H
+#define BORNAGAIN_GUI_ITEMS_MATERIALDATAITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class BA_CORE_API_ MaterialDataItem : public SessionItem {
 protected:
@@ -48,4 +48,4 @@ public:
     friend class MaterialItem;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MATERIALDATAITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_MATERIALDATAITEMS_H
diff --git a/GUI/Session/MaterialItem.cpp b/GUI/Items/MaterialItem.cpp
similarity index 97%
rename from GUI/Session/MaterialItem.cpp
rename to GUI/Items/MaterialItem.cpp
index bd930a410f94e21d0745992465ca41de29f88ab9..efaf3b07ac05fc06c4935d061cf4d81ac7196db4 100644
--- a/GUI/Session/MaterialItem.cpp
+++ b/GUI/Items/MaterialItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItem.cpp
+//! @file      GUI/Items/MaterialItem.cpp
 //! @brief     Implements class MaterialItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,13 +12,13 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MaterialItem.h"
+#include "GUI/Items/MaterialItem.h"
 #include "Base/Utils/Assert.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/MaterialDataItems.h"
+#include "GUI/Items/MaterialDataItems.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/utils/Helpers.h"
 #include "Sample/Material/MaterialFactoryFuncs.h"
 
diff --git a/GUI/Session/MaterialItem.h b/GUI/Items/MaterialItem.h
similarity index 91%
rename from GUI/Session/MaterialItem.h
rename to GUI/Items/MaterialItem.h
index 45bc9fe43bcf8df1977af0f0eca6fda0aab3fca6..730c9f93c2a19017415d258ea4c9618e50059df0 100644
--- a/GUI/Session/MaterialItem.h
+++ b/GUI/Items/MaterialItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItem.h
+//! @file      GUI/Items/MaterialItem.h
 //! @brief     Defines class MaterialItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MATERIALITEM_H
-#define BORNAGAIN_GUI_SESSION_MATERIALITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_MATERIALITEM_H
+#define BORNAGAIN_GUI_ITEMS_MATERIALITEM_H
 
 #include "Base/Types/Complex.h"
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class Material;
 class DoubleDescriptor;
@@ -73,4 +73,4 @@ public:
     bool operator!=(const MaterialItem& other) const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MATERIALITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_MATERIALITEM_H
diff --git a/GUI/Session/MaterialItemContainer.cpp b/GUI/Items/MaterialItemContainer.cpp
similarity index 90%
rename from GUI/Session/MaterialItemContainer.cpp
rename to GUI/Items/MaterialItemContainer.cpp
index e3cdb212f7fe10d0d453f4f82beb8781ca43ec71..f96c326732bac1ea21dddfde2c4b47300ba05b6b 100644
--- a/GUI/Session/MaterialItemContainer.cpp
+++ b/GUI/Items/MaterialItemContainer.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItemContainer.cpp
+//! @file      GUI/Items/MaterialItemContainer.cpp
 //! @brief     Implements class MaterialItemContainer
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/MaterialItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/MaterialItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/utils/Helpers.h"
 
 MaterialItemContainer::MaterialItemContainer() : SessionItem(M_TYPE)
diff --git a/GUI/Session/MaterialItemContainer.h b/GUI/Items/MaterialItemContainer.h
similarity index 81%
rename from GUI/Session/MaterialItemContainer.h
rename to GUI/Items/MaterialItemContainer.h
index 7512116bfb4b73e90e5e43514858c29876f406b4..5c51c512530275e083efe438aea20d5d2f12e464 100644
--- a/GUI/Session/MaterialItemContainer.h
+++ b/GUI/Items/MaterialItemContainer.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItemContainer.h
+//! @file      GUI/Items/MaterialItemContainer.h
 //! @brief     Defines class MaterialItemContainer
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MATERIALITEMCONTAINER_H
-#define BORNAGAIN_GUI_SESSION_MATERIALITEMCONTAINER_H
+#ifndef BORNAGAIN_GUI_ITEMS_MATERIALITEMCONTAINER_H
+#define BORNAGAIN_GUI_ITEMS_MATERIALITEMCONTAINER_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class MaterialItem;
 
@@ -38,4 +38,4 @@ public:
     QVector<MaterialItem*> getMaterials();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MATERIALITEMCONTAINER_H
+#endif // BORNAGAIN_GUI_ITEMS_MATERIALITEMCONTAINER_H
diff --git a/GUI/Session/MaterialItemUtils.cpp b/GUI/Items/MaterialItemUtils.cpp
similarity index 92%
rename from GUI/Session/MaterialItemUtils.cpp
rename to GUI/Items/MaterialItemUtils.cpp
index d52951d0689a1d30fb7a6f1795f063d78870467d..7968b6cfc67a3365723676b8bfa377f883b78c08 100644
--- a/GUI/Session/MaterialItemUtils.cpp
+++ b/GUI/Items/MaterialItemUtils.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItemUtils.cpp
+//! @file      GUI/Items/MaterialItemUtils.cpp
 //! @brief     Implements class MaterialItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,17 +12,17 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MaterialItemContainer.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MaterialItemContainer.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Material/MaterialModelStore.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "Sample/Material/Material.h"
 
 #include <boost/polymorphic_cast.hpp>
diff --git a/GUI/Session/MaterialItemUtils.h b/GUI/Items/MaterialItemUtils.h
similarity index 85%
rename from GUI/Session/MaterialItemUtils.h
rename to GUI/Items/MaterialItemUtils.h
index fbc1db45dd857ca3f56570df9bd186271c061e78..5b85cb85765d2b1986296ecdf113f34a8f0c12b0 100644
--- a/GUI/Session/MaterialItemUtils.h
+++ b/GUI/Items/MaterialItemUtils.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MaterialItemUtils.h
+//! @file      GUI/Items/MaterialItemUtils.h
 //! @brief     Defines namespace GUI::Model::MaterialItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MATERIALITEMUTILS_H
-#define BORNAGAIN_GUI_SESSION_MATERIALITEMUTILS_H
+#ifndef BORNAGAIN_GUI_ITEMS_MATERIALITEMUTILS_H
+#define BORNAGAIN_GUI_ITEMS_MATERIALITEMUTILS_H
 
-#include "GUI/Session/MaterialItem.h"
+#include "GUI/Items/MaterialItem.h"
 #include <QColor>
 #include <QString>
 #include <memory>
@@ -43,4 +43,4 @@ QVector<ItemWithMaterial*> itemsWithMaterial(ParticleLayoutItem* item);
 
 } // namespace GUI::Model::MaterialItemUtils
 
-#endif // BORNAGAIN_GUI_SESSION_MATERIALITEMUTILS_H
+#endif // BORNAGAIN_GUI_ITEMS_MATERIALITEMUTILS_H
diff --git a/GUI/Session/MesoCrystalItem.cpp b/GUI/Items/MesoCrystalItem.cpp
similarity index 94%
rename from GUI/Session/MesoCrystalItem.cpp
rename to GUI/Items/MesoCrystalItem.cpp
index 37406e813dbf4197eee9bd3bf4539c06b4556132..c34880cca25d7c75b74ed4a5fa7bd6408a744121 100644
--- a/GUI/Session/MesoCrystalItem.cpp
+++ b/GUI/Items/MesoCrystalItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MesoCrystalItem.cpp
+//! @file      GUI/Items/MesoCrystalItem.cpp
 //! @brief     Implements class MesoCrystalItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,17 +12,17 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MesoCrystalItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FormFactorItems.h"
+#include "GUI/Items/FormFactorItems.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Sample/Particle/Crystal.h"
 #include "Sample/Particle/MesoCrystal.h"
 #include "Sample/Particle/Particle.h"
diff --git a/GUI/Session/MesoCrystalItem.h b/GUI/Items/MesoCrystalItem.h
similarity index 90%
rename from GUI/Session/MesoCrystalItem.h
rename to GUI/Items/MesoCrystalItem.h
index 28a1ebc959595f2dd5d8c6ede7776329052c13d2..61574f3327aa80c1da2be5f5671395a421e7958c 100644
--- a/GUI/Session/MesoCrystalItem.h
+++ b/GUI/Items/MesoCrystalItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MesoCrystalItem.h
+//! @file      GUI/Items/MesoCrystalItem.h
 //! @brief     Defines class MesoCrystalItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,13 +12,13 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MESOCRYSTALITEM_H
-#define BORNAGAIN_GUI_SESSION_MESOCRYSTALITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_MESOCRYSTALITEM_H
+#define BORNAGAIN_GUI_ITEMS_MESOCRYSTALITEM_H
 
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/ItemWithParticles.h"
+#include "GUI/Items/ItemWithParticles.h"
 #include "GUI/Models/Group/SelectionDescriptor.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "Sample/Lattice/Lattice3D.h"
 
 class FormFactorItem;
@@ -82,4 +82,4 @@ template <typename T> T* MesoCrystalItem::createBasis()
     return model()->insertItem<T>(this, -1, T_BASIS_PARTICLE);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_MESOCRYSTALITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_MESOCRYSTALITEM_H
diff --git a/GUI/Session/MinimizerItem.cpp b/GUI/Items/MinimizerItem.cpp
similarity index 98%
rename from GUI/Session/MinimizerItem.cpp
rename to GUI/Items/MinimizerItem.cpp
index e5bbac10b7783615c19cc82456f29466ced6dad0..6e162156aaf82dd4442a570a7bf6824ac4f06e0a 100644
--- a/GUI/Session/MinimizerItem.cpp
+++ b/GUI/Items/MinimizerItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MinimizerItem.cpp
+//! @file      GUI/Items/MinimizerItem.cpp
 //! @brief     Implements MinimizerItem class
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MinimizerItem.h"
+#include "GUI/Items/MinimizerItem.h"
 #include "Core/Fitting/ObjectiveMetric.h"
 #include "Core/Fitting/ObjectiveMetricUtils.h"
 #include "Fit/Adapter/GSLLevenbergMarquardtMinimizer.h"
@@ -22,7 +22,7 @@
 #include "Fit/Adapter/SimAnMinimizer.h"
 #include "Fit/Minimizer/TestMinimizer.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/MinimizerItemCatalog.h"
+#include "GUI/Items/MinimizerItemCatalog.h"
 
 namespace {
 
diff --git a/GUI/Session/MinimizerItem.h b/GUI/Items/MinimizerItem.h
similarity index 95%
rename from GUI/Session/MinimizerItem.h
rename to GUI/Items/MinimizerItem.h
index aa05114e91c6053c3da8c83da4d3ec958f97abcc..6a582c60dbc5d4111275b3c65956ea3cf9e3ce2e 100644
--- a/GUI/Session/MinimizerItem.h
+++ b/GUI/Items/MinimizerItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MinimizerItem.h
+//! @file      GUI/Items/MinimizerItem.h
 //! @brief     Defines MinimizerItem class
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MINIMIZERITEM_H
-#define BORNAGAIN_GUI_SESSION_MINIMIZERITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_MINIMIZERITEM_H
+#define BORNAGAIN_GUI_ITEMS_MINIMIZERITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IMinimizer;
 class ObjectiveMetric;
@@ -139,4 +139,4 @@ public:
     std::unique_ptr<IMinimizer> createMinimizer() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MINIMIZERITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_MINIMIZERITEM_H
diff --git a/GUI/Session/MinimizerItemCatalog.cpp b/GUI/Items/MinimizerItemCatalog.cpp
similarity index 94%
rename from GUI/Session/MinimizerItemCatalog.cpp
rename to GUI/Items/MinimizerItemCatalog.cpp
index 62889bb6a16b1c6802729bf3ea87d48064c38f3f..49a2813c051da50b202859c14566a41457ca5274 100644
--- a/GUI/Session/MinimizerItemCatalog.cpp
+++ b/GUI/Items/MinimizerItemCatalog.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MinimizerItemCatalog.cpp
+//! @file      GUI/Items/MinimizerItemCatalog.cpp
 //! @brief     Implements MinimizerItemCatalog class
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MinimizerItemCatalog.h"
+#include "GUI/Items/MinimizerItemCatalog.h"
 #include "Fit/Kernel/MinimizerFactory.h"
 #include "GUI/utils/Helpers.h"
 
diff --git a/GUI/Session/MinimizerItemCatalog.h b/GUI/Items/MinimizerItemCatalog.h
similarity index 83%
rename from GUI/Session/MinimizerItemCatalog.h
rename to GUI/Items/MinimizerItemCatalog.h
index f681818a72428d573b9cf8bb3511407d154efbc4..e7f2afea186ad3570da1a3d60a61c21665d88c10 100644
--- a/GUI/Session/MinimizerItemCatalog.h
+++ b/GUI/Items/MinimizerItemCatalog.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MinimizerItemCatalog.h
+//! @file      GUI/Items/MinimizerItemCatalog.h
 //! @brief     Defines MinimizerItemCatalog class
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MINIMIZERITEMCATALOG_H
-#define BORNAGAIN_GUI_SESSION_MINIMIZERITEMCATALOG_H
+#ifndef BORNAGAIN_GUI_ITEMS_MINIMIZERITEMCATALOG_H
+#define BORNAGAIN_GUI_ITEMS_MINIMIZERITEMCATALOG_H
 
 #include "GUI/Models/Group/ComboProperty.h"
 
@@ -31,4 +31,4 @@ private:
     static QStringList algorithmDescriptions(const QString& minimizerType);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MINIMIZERITEMCATALOG_H
+#endif // BORNAGAIN_GUI_ITEMS_MINIMIZERITEMCATALOG_H
diff --git a/GUI/Session/ModelPath.cpp b/GUI/Items/ModelPath.cpp
similarity index 95%
rename from GUI/Session/ModelPath.cpp
rename to GUI/Items/ModelPath.cpp
index f88796c862e5690c0957ef3a76fb1eb61f31f78d..ff5dc7d73b090bec940e582b94bcc41cc02e4f87 100644
--- a/GUI/Session/ModelPath.cpp
+++ b/GUI/Items/ModelPath.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ModelPath.cpp
+//! @file      GUI/Items/ModelPath.cpp
 //! @brief     Implements class ModelPath
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/JobItem.h"
 
 QString GUI::Model::Path::getPathFromIndex(const QModelIndex& index)
 {
diff --git a/GUI/Session/ModelPath.h b/GUI/Items/ModelPath.h
similarity index 87%
rename from GUI/Session/ModelPath.h
rename to GUI/Items/ModelPath.h
index 72822d85076b41256523c0d53ff1b055ccc631da..8e99e1aeb3727baee69d8146f06f259807f08d3f 100644
--- a/GUI/Session/ModelPath.h
+++ b/GUI/Items/ModelPath.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ModelPath.h
+//! @file      GUI/Items/ModelPath.h
 //! @brief     Defines namespace GUI::Model::Path
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MODELPATH_H
-#define BORNAGAIN_GUI_SESSION_MODELPATH_H
+#ifndef BORNAGAIN_GUI_ITEMS_MODELPATH_H
+#define BORNAGAIN_GUI_ITEMS_MODELPATH_H
 
 #include <memory>
 #include <vector>
@@ -39,4 +39,4 @@ const SessionItem* ancestor(const SessionItem* item, const QString& requiredMode
 
 } // namespace GUI::Model::Path
 
-#endif // BORNAGAIN_GUI_SESSION_MODELPATH_H
+#endif // BORNAGAIN_GUI_ITEMS_MODELPATH_H
diff --git a/GUI/Session/MultiLayerItem.cpp b/GUI/Items/MultiLayerItem.cpp
similarity index 95%
rename from GUI/Session/MultiLayerItem.cpp
rename to GUI/Items/MultiLayerItem.cpp
index e059d926b266d98b6e6f3c3ca2d1cee4ed522312..68f90b5b1335c7c1c25a089547b423913f0e357a 100644
--- a/GUI/Session/MultiLayerItem.cpp
+++ b/GUI/Items/MultiLayerItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MultiLayerItem.cpp
+//! @file      GUI/Items/MultiLayerItem.cpp
 //! @brief     Implements class MultiLayerItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 namespace {
 const QString external_field_tooltip = "External field (A/m)";
diff --git a/GUI/Session/MultiLayerItem.h b/GUI/Items/MultiLayerItem.h
similarity index 89%
rename from GUI/Session/MultiLayerItem.h
rename to GUI/Items/MultiLayerItem.h
index b63ae3b1bd3a24ac99ffbccf72bf4c6e0b5f063d..45fae497902ef4ad4383eb5474daab5d9c0cb50a 100644
--- a/GUI/Session/MultiLayerItem.h
+++ b/GUI/Items/MultiLayerItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/MultiLayerItem.h
+//! @file      GUI/Items/MultiLayerItem.h
 //! @brief     Defines class MultiLayerItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_MULTILAYERITEM_H
-#define BORNAGAIN_GUI_SESSION_MULTILAYERITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_MULTILAYERITEM_H
+#define BORNAGAIN_GUI_ITEMS_MULTILAYERITEM_H
 
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 class LayerItem;
 class ItemWithMaterial;
@@ -63,4 +63,4 @@ private:
     void updateLayers();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_MULTILAYERITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_MULTILAYERITEM_H
diff --git a/GUI/Session/ParameterTreeItems.cpp b/GUI/Items/ParameterTreeItems.cpp
similarity index 92%
rename from GUI/Session/ParameterTreeItems.cpp
rename to GUI/Items/ParameterTreeItems.cpp
index 54d95abce16a6ea2f14fafc68bf16b6cc9a451f8..37ccfaa14d3fabd2421a32f5b6a2c9faf3f775a1 100644
--- a/GUI/Session/ParameterTreeItems.cpp
+++ b/GUI/Items/ParameterTreeItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParameterTreeItems.cpp
+//! @file      GUI/Items/ParameterTreeItems.cpp
 //! @brief     Implements classes for ParameterTreeItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include "GUI/Models/Job/FitParameterHelper.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/SessionModel.h"
 
 // ----------------------------------------------------------------------------
 
diff --git a/GUI/Session/ParameterTreeItems.h b/GUI/Items/ParameterTreeItems.h
similarity index 87%
rename from GUI/Session/ParameterTreeItems.h
rename to GUI/Items/ParameterTreeItems.h
index fd73436f49751dd2f2940c6b964f91abe292a2d9..9e2dc59ce0c11f5982d979b5e9b806fa119c5815 100644
--- a/GUI/Session/ParameterTreeItems.h
+++ b/GUI/Items/ParameterTreeItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParameterTreeItems.h
+//! @file      GUI/Items/ParameterTreeItems.h
 //! @brief     Defines classes for ParameterTreeItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PARAMETERTREEITEMS_H
-#define BORNAGAIN_GUI_SESSION_PARAMETERTREEITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_PARAMETERTREEITEMS_H
+#define BORNAGAIN_GUI_ITEMS_PARAMETERTREEITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 //! ParameterTreeItems is a collection of items necessary to form a tuning tree for
 //! real time widget.
@@ -60,4 +60,4 @@ public:
     ParameterContainerItem();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_PARAMETERTREEITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_PARAMETERTREEITEMS_H
diff --git a/GUI/Session/ParticleCompositionItem.cpp b/GUI/Items/ParticleCompositionItem.cpp
similarity index 91%
rename from GUI/Session/ParticleCompositionItem.cpp
rename to GUI/Items/ParticleCompositionItem.cpp
index 82f319cb176a545fc08ea4d93d356a7839d0816f..3cee3c3975166a0463347a8b9d744cf8bd9961f9 100644
--- a/GUI/Session/ParticleCompositionItem.cpp
+++ b/GUI/Items/ParticleCompositionItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleCompositionItem.cpp
+//! @file      GUI/Items/ParticleCompositionItem.cpp
 //! @brief     Implements class ParticleCompositionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Sample/Particle/MesoCrystal.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Particle/ParticleCoreShell.h"
diff --git a/GUI/Session/ParticleCompositionItem.h b/GUI/Items/ParticleCompositionItem.h
similarity index 80%
rename from GUI/Session/ParticleCompositionItem.h
rename to GUI/Items/ParticleCompositionItem.h
index bcd8bbe49dd501db4953ed2d410e77377baf9ceb..a9b4fe64c8ff039205d9b2b61c56209137c6afc2 100644
--- a/GUI/Session/ParticleCompositionItem.h
+++ b/GUI/Items/ParticleCompositionItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleCompositionItem.h
+//! @file      GUI/Items/ParticleCompositionItem.h
 //! @brief     Defines class ParticleCompositionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PARTICLECOMPOSITIONITEM_H
-#define BORNAGAIN_GUI_SESSION_PARTICLECOMPOSITIONITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_PARTICLECOMPOSITIONITEM_H
+#define BORNAGAIN_GUI_ITEMS_PARTICLECOMPOSITIONITEM_H
 
-#include "GUI/Session/ItemWithParticles.h"
+#include "GUI/Items/ItemWithParticles.h"
 #include "Sample/Particle/ParticleComposition.h"
 
 class VectorItem;
@@ -36,4 +36,4 @@ public:
     void removeParticle(ItemWithParticles* particle);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_PARTICLECOMPOSITIONITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_PARTICLECOMPOSITIONITEM_H
diff --git a/GUI/Session/ParticleCoreShellItem.cpp b/GUI/Items/ParticleCoreShellItem.cpp
similarity index 92%
rename from GUI/Session/ParticleCoreShellItem.cpp
rename to GUI/Items/ParticleCoreShellItem.cpp
index 05676cfafcd2b9edbe8be5f688cee2a9953035d0..2703d03801170b6323386b8f9541c7784631d1c4 100644
--- a/GUI/Session/ParticleCoreShellItem.cpp
+++ b/GUI/Items/ParticleCoreShellItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleCoreShellItem.cpp
+//! @file      GUI/Items/ParticleCoreShellItem.cpp
 //! @brief     Implements class ParticleCoreShellItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Particle/ParticleCoreShell.h"
 
diff --git a/GUI/Session/ParticleCoreShellItem.h b/GUI/Items/ParticleCoreShellItem.h
similarity index 83%
rename from GUI/Session/ParticleCoreShellItem.h
rename to GUI/Items/ParticleCoreShellItem.h
index 0b93e62e49d6413724c1a1d1bc724b6ec9351896..f5ba427c14ee89326b0ccb02c4e7e52d2a9386ff 100644
--- a/GUI/Session/ParticleCoreShellItem.h
+++ b/GUI/Items/ParticleCoreShellItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleCoreShellItem.h
+//! @file      GUI/Items/ParticleCoreShellItem.h
 //! @brief     Defines class ParticleCoreShellItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PARTICLECORESHELLITEM_H
-#define BORNAGAIN_GUI_SESSION_PARTICLECORESHELLITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_PARTICLECORESHELLITEM_H
+#define BORNAGAIN_GUI_ITEMS_PARTICLECORESHELLITEM_H
 
-#include "GUI/Session/ItemWithParticles.h"
+#include "GUI/Items/ItemWithParticles.h"
 
 class ParticleCoreShell;
 class ParticleItem;
@@ -44,4 +44,4 @@ public:
     static bool isShellTagName(const QString& name);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_PARTICLECORESHELLITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_PARTICLECORESHELLITEM_H
diff --git a/GUI/Session/ParticleItem.cpp b/GUI/Items/ParticleItem.cpp
similarity index 88%
rename from GUI/Session/ParticleItem.cpp
rename to GUI/Items/ParticleItem.cpp
index 54b0b0714e461c8d87a61299c1115e9d7145687d..ce6912843450fb2d9758fc9e53c2a1f75cd003f6 100644
--- a/GUI/Session/ParticleItem.cpp
+++ b/GUI/Items/ParticleItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleItem.cpp
+//! @file      GUI/Items/ParticleItem.cpp
 //! @brief     Implements class ParticleItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,15 +12,15 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/MaterialItemUtils.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/MaterialItemUtils.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Scattering/IFormFactor.h"
 
diff --git a/GUI/Session/ParticleItem.h b/GUI/Items/ParticleItem.h
similarity index 85%
rename from GUI/Session/ParticleItem.h
rename to GUI/Items/ParticleItem.h
index bea437e8e6085f3dd7aaec0aac4df70a593c20e4..6cb19470dd01c4e0938807d94703692e3a6c42f7 100644
--- a/GUI/Session/ParticleItem.h
+++ b/GUI/Items/ParticleItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleItem.h
+//! @file      GUI/Items/ParticleItem.h
 //! @brief     Defines class ParticleItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PARTICLEITEM_H
-#define BORNAGAIN_GUI_SESSION_PARTICLEITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_PARTICLEITEM_H
+#define BORNAGAIN_GUI_ITEMS_PARTICLEITEM_H
 
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/ItemWithParticles.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/ItemWithParticles.h"
 
 class FormFactorItem;
 class GroupItem;
@@ -53,4 +53,4 @@ template <typename T> T* ParticleItem::setFormFactorType()
     return setGroupPropertyType<T>(P_FORM_FACTOR);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_PARTICLEITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_PARTICLEITEM_H
diff --git a/GUI/Session/ParticleLayoutItem.cpp b/GUI/Items/ParticleLayoutItem.cpp
similarity index 93%
rename from GUI/Session/ParticleLayoutItem.cpp
rename to GUI/Items/ParticleLayoutItem.cpp
index 1bed60d5e497d8d91e1eb2ed68ba5eaccb9534f8..8b630763c0479ff7346a70024357df167d023f48 100644
--- a/GUI/Session/ParticleLayoutItem.cpp
+++ b/GUI/Items/ParticleLayoutItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleLayoutItem.cpp
+//! @file      GUI/Items/ParticleLayoutItem.cpp
 //! @brief     Implements class ParticleLayoutItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,16 +12,16 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/ItemCatalog.h"
-#include "GUI/Session/Lattice2DItems.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/ItemCatalog.h"
+#include "GUI/Items/Lattice2DItems.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionModel.h"
 
 namespace {
 
diff --git a/GUI/Session/ParticleLayoutItem.h b/GUI/Items/ParticleLayoutItem.h
similarity index 86%
rename from GUI/Session/ParticleLayoutItem.h
rename to GUI/Items/ParticleLayoutItem.h
index d03b96658cc3d304e2b4f2cfb23e39eaaa1c4ec3..c200d6cd5314aa1895c965f7869e8f1569ce7c64 100644
--- a/GUI/Session/ParticleLayoutItem.h
+++ b/GUI/Items/ParticleLayoutItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ParticleLayoutItem.h
+//! @file      GUI/Items/ParticleLayoutItem.h
 //! @brief     Defines class ParticleLayoutItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PARTICLELAYOUTITEM_H
-#define BORNAGAIN_GUI_SESSION_PARTICLELAYOUTITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_PARTICLELAYOUTITEM_H
+#define BORNAGAIN_GUI_ITEMS_PARTICLELAYOUTITEM_H
 
 #include "GUI/Models/Group/SelectionDescriptor.h"
-#include "GUI/Session/SessionGraphicsItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionGraphicsItem.h"
+#include "GUI/Items/SessionModel.h"
 
 class InterferenceItem;
 class ItemWithParticles;
@@ -59,4 +59,4 @@ template <typename T> T* ParticleLayoutItem::createInterference()
     return model()->insertItem<T>(this, -1, T_INTERFERENCE);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_PARTICLELAYOUTITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_PARTICLELAYOUTITEM_H
diff --git a/GUI/Session/PointwiseAxisItem.cpp b/GUI/Items/PointwiseAxisItem.cpp
similarity index 97%
rename from GUI/Session/PointwiseAxisItem.cpp
rename to GUI/Items/PointwiseAxisItem.cpp
index 9cb4b21ebe616bc77724ce83e28286c834c21c90..6e9b263486a13576e4a9c4f79a3809efce1eb29d 100644
--- a/GUI/Session/PointwiseAxisItem.cpp
+++ b/GUI/Items/PointwiseAxisItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/PointwiseAxisItem.cpp
+//! @file      GUI/Items/PointwiseAxisItem.cpp
 //! @brief     Implements pointwise axis item
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/PointwiseAxisItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
 #include "Base/Axis/PointwiseAxis.h"
 #include "Device/Coord/ICoordSystem.h"
 #include "Device/Data/OutputData.h"
 #include "Device/Histo/IntensityDataIOFactory.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 
 namespace {
 
diff --git a/GUI/Session/PointwiseAxisItem.h b/GUI/Items/PointwiseAxisItem.h
similarity index 89%
rename from GUI/Session/PointwiseAxisItem.h
rename to GUI/Items/PointwiseAxisItem.h
index da4a804470cfb7ad2d52189ed043b7efb682be9c..94ca4d8f6ac258f0018eaf6eae52691a061c621d 100644
--- a/GUI/Session/PointwiseAxisItem.h
+++ b/GUI/Items/PointwiseAxisItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/PointwiseAxisItem.h
+//! @file      GUI/Items/PointwiseAxisItem.h
 //! @brief     Defines pointwise axis item
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_POINTWISEAXISITEM_H
-#define BORNAGAIN_GUI_SESSION_POINTWISEAXISITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_POINTWISEAXISITEM_H
+#define BORNAGAIN_GUI_ITEMS_POINTWISEAXISITEM_H
 
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/utils/SaveLoadInterface.h"
 
 class PointwiseAxis;
@@ -63,4 +63,4 @@ private:
     QDateTime m_last_modified;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_POINTWISEAXISITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_POINTWISEAXISITEM_H
diff --git a/GUI/Session/ProjectionItems.cpp b/GUI/Items/ProjectionItems.cpp
similarity index 87%
rename from GUI/Session/ProjectionItems.cpp
rename to GUI/Items/ProjectionItems.cpp
index f6a8a6b05c3b37a883178dabfeeddbe1ef00a6a2..07b26b4f7d830ea40a40e5db876ec86e33b3558a 100644
--- a/GUI/Session/ProjectionItems.cpp
+++ b/GUI/Items/ProjectionItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ProjectionItems.cpp
+//! @file      GUI/Items/ProjectionItems.cpp
 //! @brief     Implements items related to projections over color map.
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ProjectionItems.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
+#include "GUI/Items/MaskItems.h"
 
 ProjectionContainerItem::ProjectionContainerItem() : SessionItem(M_TYPE)
 {
diff --git a/GUI/Session/ProjectionItems.h b/GUI/Items/ProjectionItems.h
similarity index 78%
rename from GUI/Session/ProjectionItems.h
rename to GUI/Items/ProjectionItems.h
index 085be3339ac061e196fa0d7df7b2da8f219708a0..97bbe18d7a522612461cc2d70cffda78e4666deb 100644
--- a/GUI/Session/ProjectionItems.h
+++ b/GUI/Items/ProjectionItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ProjectionItems.h
+//! @file      GUI/Items/ProjectionItems.h
 //! @brief     Defines items related to projections over color map.
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PROJECTIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_PROJECTIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_PROJECTIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_PROJECTIONITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 //! A container to hold ProjectionItems, intended to store projections of color map on X, Y axes.
 
@@ -26,4 +26,4 @@ public:
     ProjectionContainerItem();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_PROJECTIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_PROJECTIONITEMS_H
diff --git a/GUI/Session/PropertyItem.cpp b/GUI/Items/PropertyItem.cpp
similarity index 88%
rename from GUI/Session/PropertyItem.cpp
rename to GUI/Items/PropertyItem.cpp
index 2af5b1e8dfe90f4dabe317b7450355c6034c16d0..037399412b0fecd11076d5350c6206087c569f48 100644
--- a/GUI/Session/PropertyItem.cpp
+++ b/GUI/Items/PropertyItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/PropertyItem.cpp
+//! @file      GUI/Items/PropertyItem.cpp
 //! @brief     Implements class PropertyItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,6 +12,6 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/PropertyItem.h"
+#include "GUI/Items/PropertyItem.h"
 
 PropertyItem::PropertyItem() : SessionItem(M_TYPE) {}
diff --git a/GUI/Session/PropertyItem.h b/GUI/Items/PropertyItem.h
similarity index 76%
rename from GUI/Session/PropertyItem.h
rename to GUI/Items/PropertyItem.h
index 35243812fbd2a60148c8a642f7471942c628d8cb..c93c68c76f690e0b3625635b567d20f71c47f77b 100644
--- a/GUI/Session/PropertyItem.h
+++ b/GUI/Items/PropertyItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/PropertyItem.h
+//! @file      GUI/Items/PropertyItem.h
 //! @brief     Defines class PropertyItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_PROPERTYITEM_H
-#define BORNAGAIN_GUI_SESSION_PROPERTYITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_PROPERTYITEM_H
+#define BORNAGAIN_GUI_ITEMS_PROPERTYITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class BA_CORE_API_ PropertyItem : public SessionItem {
 
@@ -25,4 +25,4 @@ public:
     PropertyItem();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_PROPERTYITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_PROPERTYITEM_H
diff --git a/GUI/Session/RealDataItem.cpp b/GUI/Items/RealDataItem.cpp
similarity index 96%
rename from GUI/Session/RealDataItem.cpp
rename to GUI/Items/RealDataItem.cpp
index 5da139490b731d0fa2d2bd255e0fa76ac2b02810..3649e4b6c0d6b5ff5a36637100ae94ecd26e6cdb 100644
--- a/GUI/Session/RealDataItem.cpp
+++ b/GUI/Items/RealDataItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RealDataItem.cpp
+//! @file      GUI/Items/RealDataItem.cpp
 //! @brief     Implements class RealDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,24 +12,24 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "Device/Data/DataUtils.h"
 #include "GUI/Models/Data/AbstractDataLoader1D.h"
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/Models/Data/DataLoaders1D.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Data/ImportDataInfo.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/JobModelFunctions.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/JobModelFunctions.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Models/Data/RealDataModel.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Project/projectmanager.h"
 #include "GUI/utils/DeserializationException.h"
 #include <QtCore/QXmlStreamReader>
diff --git a/GUI/Session/RealDataItem.h b/GUI/Items/RealDataItem.h
similarity index 94%
rename from GUI/Session/RealDataItem.h
rename to GUI/Items/RealDataItem.h
index f2bc310ccaede6be67293834d72606da8912ea1e..dfbd0d18a26fd42e9f97253e55e65ab374361ce8 100644
--- a/GUI/Session/RealDataItem.h
+++ b/GUI/Items/RealDataItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RealDataItem.h
+//! @file      GUI/Items/RealDataItem.h
 //! @brief     Defines class RealDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_REALDATAITEM_H
-#define BORNAGAIN_GUI_SESSION_REALDATAITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_REALDATAITEM_H
+#define BORNAGAIN_GUI_ITEMS_REALDATAITEM_H
 
 #include "GUI/Models/Data/AbstractDataLoader.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <QPointer>
 
 class DataItem;
@@ -127,4 +127,4 @@ private:
     std::unique_ptr<AbstractDataLoader> m_dataLoader;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_REALDATAITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_REALDATAITEM_H
diff --git a/GUI/Session/RealLimitsItems.cpp b/GUI/Items/RealLimitsItems.cpp
similarity index 97%
rename from GUI/Session/RealLimitsItems.cpp
rename to GUI/Items/RealLimitsItems.cpp
index d024304765eee56fabc8530897013acf68a0c40f..e55bd157f0458c3c2bd0b21b3fe0195c71d4fbba 100644
--- a/GUI/Session/RealLimitsItems.cpp
+++ b/GUI/Items/RealLimitsItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RealLimitsItems.cpp
+//! @file      GUI/Items/RealLimitsItems.cpp
 //! @brief     Defines RealLimitsItems's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/RealLimitsItems.h"
+#include "GUI/Items/RealLimitsItems.h"
 
 namespace {
 const QString tooltip_min_value = "Minimum allowed value, value included.";
diff --git a/GUI/Session/RealLimitsItems.h b/GUI/Items/RealLimitsItems.h
similarity index 91%
rename from GUI/Session/RealLimitsItems.h
rename to GUI/Items/RealLimitsItems.h
index 2005c47c8aa4d1ee9299b5f0133f61d85ae71308..1a208165fed65f52390c789bc0db9714d8ce41a0 100644
--- a/GUI/Session/RealLimitsItems.h
+++ b/GUI/Items/RealLimitsItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RealLimitsItems.h
+//! @file      GUI/Items/RealLimitsItems.h
 //! @brief     Defines RealLimitsItems's classes
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_REALLIMITSITEMS_H
-#define BORNAGAIN_GUI_SESSION_REALLIMITSITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_REALLIMITSITEMS_H
+#define BORNAGAIN_GUI_ITEMS_REALLIMITSITEMS_H
 
 #include <optional>
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class RealLimitsItem : public SessionItem {
 private:
@@ -89,4 +89,4 @@ public:
     using RealLimitsItem::setUpperLimit;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_REALLIMITSITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_REALLIMITSITEMS_H
diff --git a/GUI/Session/RectangularDetectorItem.cpp b/GUI/Items/RectangularDetectorItem.cpp
similarity index 98%
rename from GUI/Session/RectangularDetectorItem.cpp
rename to GUI/Items/RectangularDetectorItem.cpp
index 18e8b6048e8d8608c13b1ea4e748450fe44d42b6..0bb3ca10e569da4e379e26be625da5e68b172c2b 100644
--- a/GUI/Session/RectangularDetectorItem.cpp
+++ b/GUI/Items/RectangularDetectorItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RectangularDetectorItem.cpp
+//! @file      GUI/Items/RectangularDetectorItem.cpp
 //! @brief     Implements class RectangularDetectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/RectangularDetectorItem.h"
+#include "GUI/Items/RectangularDetectorItem.h"
 #include "Device/Detector/RectangularDetector.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 namespace {
 const double default_detector_width = 20.0;
diff --git a/GUI/Session/RectangularDetectorItem.h b/GUI/Items/RectangularDetectorItem.h
similarity index 91%
rename from GUI/Session/RectangularDetectorItem.h
rename to GUI/Items/RectangularDetectorItem.h
index 2bf7f7cf607ae3629c8bd3d06ec450543c1cd8b6..3f2af6e1fb28402fc7d4c52b7362e5222ad868aa 100644
--- a/GUI/Session/RectangularDetectorItem.h
+++ b/GUI/Items/RectangularDetectorItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RectangularDetectorItem.h
+//! @file      GUI/Items/RectangularDetectorItem.h
 //! @brief     Defines class RectangularDetectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_RECTANGULARDETECTORITEM_H
-#define BORNAGAIN_GUI_SESSION_RECTANGULARDETECTORITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_RECTANGULARDETECTORITEM_H
+#define BORNAGAIN_GUI_ITEMS_RECTANGULARDETECTORITEM_H
 
 #include "Base/Vector/Vectors3D.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/DetectorItems.h"
+#include "GUI/Items/DetectorItems.h"
 
 class BasicAxisItem;
 class VectorItem;
@@ -92,4 +92,4 @@ private:
     bool m_is_constructed;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_RECTANGULARDETECTORITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_RECTANGULARDETECTORITEM_H
diff --git a/GUI/Session/ResolutionFunctionItems.cpp b/GUI/Items/ResolutionFunctionItems.cpp
similarity index 96%
rename from GUI/Session/ResolutionFunctionItems.cpp
rename to GUI/Items/ResolutionFunctionItems.cpp
index 4a67cb59c61b2760ff93bde3c73928eb1edca1f7..609a067a48ae955f320fb00e4a5ba419cba8dee8 100644
--- a/GUI/Session/ResolutionFunctionItems.cpp
+++ b/GUI/Items/ResolutionFunctionItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ResolutionFunctionItems.cpp
+//! @file      GUI/Items/ResolutionFunctionItems.cpp
 //! @brief     Implements family of ResolutionFunctionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/ResolutionFunctionItems.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
 #include "Device/Resolution/ResolutionFunction2DGaussian.h"
 
 ResolutionFunctionItem::ResolutionFunctionItem(const QString& name) : SessionItem(name) {}
diff --git a/GUI/Session/ResolutionFunctionItems.h b/GUI/Items/ResolutionFunctionItems.h
similarity index 87%
rename from GUI/Session/ResolutionFunctionItems.h
rename to GUI/Items/ResolutionFunctionItems.h
index 1bc8b8fb513e706deefc4a91c1b0a733e3da8036..f71ae177c5b7bd7d21a85fe38e11239cd3f72206 100644
--- a/GUI/Session/ResolutionFunctionItems.h
+++ b/GUI/Items/ResolutionFunctionItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/ResolutionFunctionItems.h
+//! @file      GUI/Items/ResolutionFunctionItems.h
 //! @brief     Defines family of ResolutionFunctionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_RESOLUTIONFUNCTIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_RESOLUTIONFUNCTIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_RESOLUTIONFUNCTIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_RESOLUTIONFUNCTIONITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <memory>
 
 class IResolutionFunction2D;
@@ -61,4 +61,4 @@ public:
     void setSigmaY(double sigma_y);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_RESOLUTIONFUNCTIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_RESOLUTIONFUNCTIONITEMS_H
diff --git a/GUI/Session/RotationItems.cpp b/GUI/Items/RotationItems.cpp
similarity index 97%
rename from GUI/Session/RotationItems.cpp
rename to GUI/Items/RotationItems.cpp
index de8e51aa22c0be719308e88684ed5dface5d1973..11c2af95fb5c3ef7ed9f46f9b0ba630f84269328 100644
--- a/GUI/Session/RotationItems.cpp
+++ b/GUI/Items/RotationItems.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RotationItems.cpp
+//! @file      GUI/Items/RotationItems.cpp
 //! @brief     Implements class RotationItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/RotationItems.h"
+#include "GUI/Items/RotationItems.h"
 #include "Base/Const/Units.h"
 #include "Base/Vector/Transform3D.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
diff --git a/GUI/Session/RotationItems.h b/GUI/Items/RotationItems.h
similarity index 90%
rename from GUI/Session/RotationItems.h
rename to GUI/Items/RotationItems.h
index 9ca5b0125b563552ad35a17a19ebe76f00fd7b0b..b08b1e76deb18130a7a4c769a30b010f2d74d585 100644
--- a/GUI/Session/RotationItems.h
+++ b/GUI/Items/RotationItems.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/RotationItems.h
+//! @file      GUI/Items/RotationItems.h
 //! @brief     Defines class RotationItems
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_ROTATIONITEMS_H
-#define BORNAGAIN_GUI_SESSION_ROTATIONITEMS_H
+#ifndef BORNAGAIN_GUI_ITEMS_ROTATIONITEMS_H
+#define BORNAGAIN_GUI_ITEMS_ROTATIONITEMS_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class IRotation;
 class Transform3D;
@@ -92,4 +92,4 @@ protected:
     virtual unique_ptr<IRotation> createRotation() const override;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_ROTATIONITEMS_H
+#endif // BORNAGAIN_GUI_ITEMS_ROTATIONITEMS_H
diff --git a/GUI/Session/SessionDecorationModel.cpp b/GUI/Items/SessionDecorationModel.cpp
similarity index 94%
rename from GUI/Session/SessionDecorationModel.cpp
rename to GUI/Items/SessionDecorationModel.cpp
index b96e4c02b311c158e478da90a324d2bb117b9a0a..8079db8f33bf4f1ff96ab5d7491686afb46e371d 100644
--- a/GUI/Session/SessionDecorationModel.cpp
+++ b/GUI/Items/SessionDecorationModel.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionDecorationModel.cpp
+//! @file      GUI/Items/SessionDecorationModel.cpp
 //! @brief     Defines class SessionDecorationModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionDecorationModel.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionDecorationModel.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/SessionModel.h"
 #include <QColor>
 #include <QIcon>
 #include <QPixmap>
diff --git a/GUI/Session/SessionDecorationModel.h b/GUI/Items/SessionDecorationModel.h
similarity index 85%
rename from GUI/Session/SessionDecorationModel.h
rename to GUI/Items/SessionDecorationModel.h
index f311f1f548429f115421bb884ddb2d3bd6e2b53a..c890577169abd4042668b7011a62542cf46fada6 100644
--- a/GUI/Session/SessionDecorationModel.h
+++ b/GUI/Items/SessionDecorationModel.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionDecorationModel.h
+//! @file      GUI/Items/SessionDecorationModel.h
 //! @brief     Defines class SessionDecorationModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONDECORATIONMODEL_H
-#define BORNAGAIN_GUI_SESSION_SESSIONDECORATIONMODEL_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONDECORATIONMODEL_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONDECORATIONMODEL_H
 
 #include <QIdentityProxyModel>
 
@@ -40,4 +40,4 @@ private:
     SessionModel* m_model;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONDECORATIONMODEL_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONDECORATIONMODEL_H
diff --git a/GUI/Session/SessionFlags.h b/GUI/Items/SessionFlags.h
similarity index 88%
rename from GUI/Session/SessionFlags.h
rename to GUI/Items/SessionFlags.h
index 07fd023e54897bc3d6347ca07a8dadf9cbfcb146..2904b706d1e58e61275621a728576d549a6cba62 100644
--- a/GUI/Session/SessionFlags.h
+++ b/GUI/Items/SessionFlags.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionFlags.h
+//! @file      GUI/Items/SessionFlags.h
 //! @brief     Defines class SessionFlags
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONFLAGS_H
-#define BORNAGAIN_GUI_SESSION_SESSIONFLAGS_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONFLAGS_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONFLAGS_H
 
 #include <qnamespace.h>
 
@@ -47,4 +47,4 @@ Q_DECLARE_OPERATORS_FOR_FLAGS(SessionFlags::ModelColumn)
 Q_DECLARE_OPERATORS_FOR_FLAGS(SessionFlags::ItemDataRole)
 Q_DECLARE_OPERATORS_FOR_FLAGS(SessionFlags::ItemAppearance)
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONFLAGS_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONFLAGS_H
diff --git a/GUI/Session/SessionGraphicsItem.cpp b/GUI/Items/SessionGraphicsItem.cpp
similarity index 93%
rename from GUI/Session/SessionGraphicsItem.cpp
rename to GUI/Items/SessionGraphicsItem.cpp
index 5e514ae588b4bd2538bf080ef1ebf3b9f633fb16..c8a2b9a7a08224598844a204effad347969f6ecb 100644
--- a/GUI/Session/SessionGraphicsItem.cpp
+++ b/GUI/Items/SessionGraphicsItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionGraphicsItem.cpp
+//! @file      GUI/Items/SessionGraphicsItem.cpp
 //! @brief     Implements class SessionGraphicsItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 SessionGraphicsItem::SessionGraphicsItem(const QString& model_type) : SessionItem(model_type)
 {
diff --git a/GUI/Session/SessionGraphicsItem.h b/GUI/Items/SessionGraphicsItem.h
similarity index 80%
rename from GUI/Session/SessionGraphicsItem.h
rename to GUI/Items/SessionGraphicsItem.h
index e8529c1820af5e244eb9c4be49a67cbf3ee6f55e..633baf74383105982267cf8000d469ba94fd3366 100644
--- a/GUI/Session/SessionGraphicsItem.h
+++ b/GUI/Items/SessionGraphicsItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionGraphicsItem.h
+//! @file      GUI/Items/SessionGraphicsItem.h
 //! @brief     Defines class SessionGraphicsItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONGRAPHICSITEM_H
-#define BORNAGAIN_GUI_SESSION_SESSIONGRAPHICSITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONGRAPHICSITEM_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONGRAPHICSITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class BA_CORE_API_ SessionGraphicsItem : public SessionItem {
 
@@ -36,4 +36,4 @@ protected:
     explicit SessionGraphicsItem(const QString& model_type);
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONGRAPHICSITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONGRAPHICSITEM_H
diff --git a/GUI/Session/SessionItem.cpp b/GUI/Items/SessionItem.cpp
similarity index 97%
rename from GUI/Session/SessionItem.cpp
rename to GUI/Items/SessionItem.cpp
index 79169b92a9e03357f5800585d082ce1647255602..7889352c4a318cb67e5e28b77fc7b5a3b7266696 100644
--- a/GUI/Session/SessionItem.cpp
+++ b/GUI/Items/SessionItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItem.cpp
+//! @file      GUI/Items/SessionItem.cpp
 //! @brief     Implements class SessionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,14 +12,14 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ItemFactory.h"
-#include "GUI/Session/ParameterTreeItems.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionItemData.h"
-#include "GUI/Session/SessionItemTags.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ItemFactory.h"
+#include "GUI/Items/ParameterTreeItems.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionItemData.h"
+#include "GUI/Items/SessionItemTags.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 
 //! Constructs new item with given model type. The type must be defined.
 SessionItem::SessionItem(const QString& modelType)
diff --git a/GUI/Session/SessionItem.h b/GUI/Items/SessionItem.h
similarity index 98%
rename from GUI/Session/SessionItem.h
rename to GUI/Items/SessionItem.h
index 0637e986a4621da31c7fac81acfa70c253c3e6f3..798d6517873900cc7ac5a9d57f124f7d84098da7 100644
--- a/GUI/Session/SessionItem.h
+++ b/GUI/Items/SessionItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItem.h
+//! @file      GUI/Items/SessionItem.h
 //! @brief     Defines class SessionItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONITEM_H
-#define BORNAGAIN_GUI_SESSION_SESSIONITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONITEM_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONITEM_H
 
 #include "Base/Utils/Assert.h"
 #include "Fit/Param/RealLimits.h"
@@ -423,4 +423,4 @@ template <typename T> bool SessionItem::hasModelType() const
     return modelType() == T::M_TYPE;
 }
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONITEM_H
diff --git a/GUI/Session/SessionItemData.cpp b/GUI/Items/SessionItemData.cpp
similarity index 93%
rename from GUI/Session/SessionItemData.cpp
rename to GUI/Items/SessionItemData.cpp
index 6bd62c84e3a1a3997bbea62344c750362116e1b5..fb644dfcf2359969a24b7ea6759677ab823af584 100644
--- a/GUI/Session/SessionItemData.cpp
+++ b/GUI/Items/SessionItemData.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemData.cpp
+//! @file      GUI/Items/SessionItemData.cpp
 //! @brief     Implements class SessionItemData
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionItemData.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/SessionItemData.h"
+#include "GUI/Items/SessionItemUtils.h"
 
 SessionItemData::ItemData::ItemData(int r, const QVariant& v) : role(r), data(v) {}
 
diff --git a/GUI/Session/SessionItemData.h b/GUI/Items/SessionItemData.h
similarity index 84%
rename from GUI/Session/SessionItemData.h
rename to GUI/Items/SessionItemData.h
index 1c94af80f366c27e8cd97a6ca231bcb791dc961a..63544e5dc0892dd4b5fc3b916e3997a5d8a00c38 100644
--- a/GUI/Session/SessionItemData.h
+++ b/GUI/Items/SessionItemData.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemData.h
+//! @file      GUI/Items/SessionItemData.h
 //! @brief     Defines class SessionItemData
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONITEMDATA_H
-#define BORNAGAIN_GUI_SESSION_SESSIONITEMDATA_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONITEMDATA_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONITEMDATA_H
 
 #include <QVariant>
 #include <QVector>
@@ -40,4 +40,4 @@ private:
     QVector<ItemData> m_values;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONITEMDATA_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONITEMDATA_H
diff --git a/GUI/Session/SessionItemTags.cpp b/GUI/Items/SessionItemTags.cpp
similarity index 98%
rename from GUI/Session/SessionItemTags.cpp
rename to GUI/Items/SessionItemTags.cpp
index 7262630d23fb58bf6377d0b45b992fb3b39b238d..1ad9868444ccae3fab3d9e601a68688fb82b382f 100644
--- a/GUI/Session/SessionItemTags.cpp
+++ b/GUI/Items/SessionItemTags.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemTags.cpp
+//! @file      GUI/Items/SessionItemTags.cpp
 //! @brief     Implement class SessionItemTags
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionItemTags.h"
+#include "GUI/Items/SessionItemTags.h"
 #include "GUI/utils/Error.h"
 
 //! Register tag with given parameters. Returns true in case of success. Returns
diff --git a/GUI/Session/SessionItemTags.h b/GUI/Items/SessionItemTags.h
similarity index 90%
rename from GUI/Session/SessionItemTags.h
rename to GUI/Items/SessionItemTags.h
index a973fda22a344c9f99dbc59bf7b8e37a07fa10c0..e86e9453afd7840c9a88ab2d2883eeabf822fa21 100644
--- a/GUI/Session/SessionItemTags.h
+++ b/GUI/Items/SessionItemTags.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemTags.h
+//! @file      GUI/Items/SessionItemTags.h
 //! @brief     Defines class SessionItemTags
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONITEMTAGS_H
-#define BORNAGAIN_GUI_SESSION_SESSIONITEMTAGS_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONITEMTAGS_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONITEMTAGS_H
 
 #include <QString>
 #include <QStringList>
@@ -61,4 +61,4 @@ private:
     QVector<TagInfo> m_tags;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONITEMTAGS_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONITEMTAGS_H
diff --git a/GUI/Session/SessionItemUtils.cpp b/GUI/Items/SessionItemUtils.cpp
similarity index 92%
rename from GUI/Session/SessionItemUtils.cpp
rename to GUI/Items/SessionItemUtils.cpp
index 56ee5bb9d3f0b091d91938753c399b911149d79f..3bc95f2cd3d7afda00ef43607c915741814bcf77 100644
--- a/GUI/Session/SessionItemUtils.cpp
+++ b/GUI/Items/SessionItemUtils.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemUtils.cpp
+//! @file      GUI/Items/SessionItemUtils.cpp
 //! @brief     Implements namespace SessionItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 #include <QColor>
 #include <QIcon>
 #include <QPixmap>
diff --git a/GUI/Session/SessionItemUtils.h b/GUI/Items/SessionItemUtils.h
similarity index 90%
rename from GUI/Session/SessionItemUtils.h
rename to GUI/Items/SessionItemUtils.h
index 627bfb0dcf279c97dbff8b45b0eecc2a27cfc1da..4b876d14525fcfba004180c4d4fbe7c0fda3b826 100644
--- a/GUI/Session/SessionItemUtils.h
+++ b/GUI/Items/SessionItemUtils.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionItemUtils.h
+//! @file      GUI/Items/SessionItemUtils.h
 //! @brief     Defines namespace GUI::Session::ItemUtils
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONITEMUTILS_H
-#define BORNAGAIN_GUI_SESSION_SESSIONITEMUTILS_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONITEMUTILS_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONITEMUTILS_H
 
 #include "Base/Vector/Vectors3D.h"
 #include <QString>
@@ -56,4 +56,4 @@ bool HasOwnAbundance(const SessionItem* item);
 
 } // namespace GUI::Session::ItemUtils
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONITEMUTILS_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONITEMUTILS_H
diff --git a/GUI/Session/SessionModel.cpp b/GUI/Items/SessionModel.cpp
similarity index 98%
rename from GUI/Session/SessionModel.cpp
rename to GUI/Items/SessionModel.cpp
index e47749f923743f7e27e30acba04e7663c7d5340d..afd5e555920ab3121f7473ac784c009346913b15 100644
--- a/GUI/Session/SessionModel.cpp
+++ b/GUI/Items/SessionModel.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionModel.cpp
+//! @file      GUI/Items/SessionModel.cpp
 //! @brief     Implements class SessionModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/ItemFactory.h"
-#include "GUI/Session/SessionItemTags.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/ItemFactory.h"
+#include "GUI/Items/SessionItemTags.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "GUI/utils/Helpers.h"
 #include <QFile>
 #include <QMimeData>
diff --git a/GUI/Session/SessionModel.h b/GUI/Items/SessionModel.h
similarity index 96%
rename from GUI/Session/SessionModel.h
rename to GUI/Items/SessionModel.h
index ec3118c0063f8dde490f58ed49ff90096083b43d..de36cce85d8cfe65cd1051459a766de20a82125f 100644
--- a/GUI/Session/SessionModel.h
+++ b/GUI/Items/SessionModel.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionModel.h
+//! @file      GUI/Items/SessionModel.h
 //! @brief     Defines class SessionModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,12 +12,12 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONMODEL_H
-#define BORNAGAIN_GUI_SESSION_SESSIONMODEL_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONMODEL_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONMODEL_H
 
-#include "GUI/Session/SessionFlags.h"
-#include "GUI/Session/SessionItem.h"
-#include "GUI/Session/SessionXML.h"
+#include "GUI/Items/SessionFlags.h"
+#include "GUI/Items/SessionItem.h"
+#include "GUI/Items/SessionXML.h"
 #include <QStringList>
 
 //! Base class for a GUI data collection.
@@ -217,4 +217,4 @@ inline void SessionModel::setDraggedItemType(const QString& type)
     m_dragged_item_type = type;
 }
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONMODEL_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONMODEL_H
diff --git a/GUI/Session/SessionXML.cpp b/GUI/Items/SessionXML.cpp
similarity index 98%
rename from GUI/Session/SessionXML.cpp
rename to GUI/Items/SessionXML.cpp
index 36aded837deb3efcfd1a8ffe48b61f858956ab04..be5351a226e286d5489792b7d45c497e4a087b19 100644
--- a/GUI/Session/SessionXML.cpp
+++ b/GUI/Items/SessionXML.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionXML.cpp
+//! @file      GUI/Items/SessionXML.cpp
 //! @brief     Implements reader and writer classes for SessionModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -14,10 +14,10 @@
 
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/MaterialItem.h"
-#include "GUI/Session/SessionItemTags.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/MaterialItem.h"
+#include "GUI/Items/SessionItemTags.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/utils/DeserializationException.h"
 #include "GUI/utils/MessageService.h"
 #include <QtCore/QXmlStreamWriter>
diff --git a/GUI/Session/SessionXML.h b/GUI/Items/SessionXML.h
similarity index 93%
rename from GUI/Session/SessionXML.h
rename to GUI/Items/SessionXML.h
index ed772cee48c68b2973fb7dd9c1697ae01b9406ba..7c5852e8573f9884e8aabcedb14336f35f9438d8 100644
--- a/GUI/Session/SessionXML.h
+++ b/GUI/Items/SessionXML.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SessionXML.h
+//! @file      GUI/Items/SessionXML.h
 //! @brief     Defines reader and writer classes for SessionModel
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,8 +12,8 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SESSIONXML_H
-#define BORNAGAIN_GUI_SESSION_SESSIONXML_H
+#ifndef BORNAGAIN_GUI_ITEMS_SESSIONXML_H
+#define BORNAGAIN_GUI_ITEMS_SESSIONXML_H
 
 #include <QVariant>
 
@@ -63,4 +63,4 @@ QString readProperty(QXmlStreamReader* reader, SessionItem* item,
 
 } // namespace GUI::Session::XML
 
-#endif // BORNAGAIN_GUI_SESSION_SESSIONXML_H
+#endif // BORNAGAIN_GUI_ITEMS_SESSIONXML_H
diff --git a/GUI/Session/SimulationOptionsItem.cpp b/GUI/Items/SimulationOptionsItem.cpp
similarity index 98%
rename from GUI/Session/SimulationOptionsItem.cpp
rename to GUI/Items/SimulationOptionsItem.cpp
index 6168ebc1f0d197aa3d2072b5fa4bb552add3cf24..a140220f3c702e94717dece093537ccf460a36eb 100644
--- a/GUI/Session/SimulationOptionsItem.cpp
+++ b/GUI/Items/SimulationOptionsItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SimulationOptionsItem.cpp
+//! @file      GUI/Items/SimulationOptionsItem.cpp
 //! @brief     Defines class SimulationOptionsItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "GUI/Models/Group/ComboProperty.h"
 #include <thread>
 
diff --git a/GUI/Session/SimulationOptionsItem.h b/GUI/Items/SimulationOptionsItem.h
similarity index 89%
rename from GUI/Session/SimulationOptionsItem.h
rename to GUI/Items/SimulationOptionsItem.h
index 4a19fae5ba4f9a609c5b33076fd379d91fb3b37c..bc450ee4aae9425e58b9381d458847f9c110e1b7 100644
--- a/GUI/Session/SimulationOptionsItem.h
+++ b/GUI/Items/SimulationOptionsItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SimulationOptionsItem.h
+//! @file      GUI/Items/SimulationOptionsItem.h
 //! @brief     Defines class SimulationOptionsItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SIMULATIONOPTIONSITEM_H
-#define BORNAGAIN_GUI_SESSION_SIMULATIONOPTIONSITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SIMULATIONOPTIONSITEM_H
+#define BORNAGAIN_GUI_ITEMS_SIMULATIONOPTIONSITEM_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <QMap>
 
 //! The SimulationOptionsItem class holds simulation status (run policy, number of threads,
@@ -58,4 +58,4 @@ public:
     bool includeSpecularPeak() const;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SIMULATIONOPTIONSITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SIMULATIONOPTIONSITEM_H
diff --git a/GUI/Session/SpecularBeamInclinationItem.cpp b/GUI/Items/SpecularBeamInclinationItem.cpp
similarity index 95%
rename from GUI/Session/SpecularBeamInclinationItem.cpp
rename to GUI/Items/SpecularBeamInclinationItem.cpp
index 9a548d6b23edb47db1e46bb367a71c731e61d0fe..3034ae1c82e02d402c3d79226cb687b9a0dc7a99 100644
--- a/GUI/Session/SpecularBeamInclinationItem.cpp
+++ b/GUI/Items/SpecularBeamInclinationItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SpecularBeamInclinationItem.cpp
+//! @file      GUI/Items/SpecularBeamInclinationItem.cpp
 //! @brief     Implements class SpecularBeamInclinationItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SpecularBeamInclinationItem.h"
+#include "GUI/Items/SpecularBeamInclinationItem.h"
 #include "Base/Const/Units.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/PointwiseAxisItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
 
 namespace {
 void setupDistributionMean(SessionItem* distribution);
diff --git a/GUI/Session/SpecularBeamInclinationItem.h b/GUI/Items/SpecularBeamInclinationItem.h
similarity index 83%
rename from GUI/Session/SpecularBeamInclinationItem.h
rename to GUI/Items/SpecularBeamInclinationItem.h
index 970995645613cb4aa7adc1fadbddaa69a9831f36..2aa75f1566b097260f14db3af1e9344107a76147 100644
--- a/GUI/Session/SpecularBeamInclinationItem.h
+++ b/GUI/Items/SpecularBeamInclinationItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SpecularBeamInclinationItem.h
+//! @file      GUI/Items/SpecularBeamInclinationItem.h
 //! @brief     Declares the class SpecularBeamInclinationItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SPECULARBEAMINCLINATIONITEM_H
-#define BORNAGAIN_GUI_SESSION_SPECULARBEAMINCLINATIONITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SPECULARBEAMINCLINATIONITEM_H
+#define BORNAGAIN_GUI_ITEMS_SPECULARBEAMINCLINATIONITEM_H
 
-#include "GUI/Session/BeamDistributionItem.h"
+#include "GUI/Items/BeamDistributionItem.h"
 
 class BasicAxisItem;
 class GroupItem;
@@ -47,4 +47,4 @@ private:
     static const bool m_show_mean = false;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SPECULARBEAMINCLINATIONITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SPECULARBEAMINCLINATIONITEM_H
diff --git a/GUI/Session/SpecularDataItem.cpp b/GUI/Items/SpecularDataItem.cpp
similarity index 97%
rename from GUI/Session/SpecularDataItem.cpp
rename to GUI/Items/SpecularDataItem.cpp
index 860d70c3edf532fce2152466e38db52276e4cbbf..927fc9fab2a4744bedbf0fcc9cb764a253f88746 100644
--- a/GUI/Session/SpecularDataItem.cpp
+++ b/GUI/Items/SpecularDataItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SpecularDataItem.cpp
+//! @file      GUI/Items/SpecularDataItem.cpp
 //! @brief     Implements class SpecularDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SpecularDataItem.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/SpecularDataItem.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Data/ImportDataInfo.h"
-#include "GUI/Session/JobItemUtils.h"
+#include "GUI/Items/JobItemUtils.h"
 
 namespace {
 
diff --git a/GUI/Session/SpecularDataItem.h b/GUI/Items/SpecularDataItem.h
similarity index 91%
rename from GUI/Session/SpecularDataItem.h
rename to GUI/Items/SpecularDataItem.h
index ac93734ecc0c88fb896abbdc1d7b0b12383f181c..a988f8502a4843c0ac1e5ae07c8b544549688917 100644
--- a/GUI/Session/SpecularDataItem.h
+++ b/GUI/Items/SpecularDataItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SpecularDataItem.h
+//! @file      GUI/Items/SpecularDataItem.h
 //! @brief     Defines class SpecularDataItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SPECULARDATAITEM_H
-#define BORNAGAIN_GUI_SESSION_SPECULARDATAITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SPECULARDATAITEM_H
+#define BORNAGAIN_GUI_ITEMS_SPECULARDATAITEM_H
 
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 
 class AmplitudeAxisItem;
 class BasicAxisItem;
@@ -89,4 +89,4 @@ private:
     void updateAxesZoomLevel();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SPECULARDATAITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SPECULARDATAITEM_H
diff --git a/GUI/Session/SphericalDetectorItem.cpp b/GUI/Items/SphericalDetectorItem.cpp
similarity index 95%
rename from GUI/Session/SphericalDetectorItem.cpp
rename to GUI/Items/SphericalDetectorItem.cpp
index f8532d1f6d392f146e9910d0bc5e35f69e90625f..1192401b29737fd31cd7783da66a69367b27f50c 100644
--- a/GUI/Session/SphericalDetectorItem.cpp
+++ b/GUI/Items/SphericalDetectorItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SphericalDetectorItem.cpp
+//! @file      GUI/Items/SphericalDetectorItem.cpp
 //! @brief     Implements class SphericalDetectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 #include "Base/Const/Units.h"
 #include "Device/Detector/SphericalDetector.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 
 SphericalDetectorItem::SphericalDetectorItem() : DetectorItem(M_TYPE)
 {
diff --git a/GUI/Session/SphericalDetectorItem.h b/GUI/Items/SphericalDetectorItem.h
similarity index 83%
rename from GUI/Session/SphericalDetectorItem.h
rename to GUI/Items/SphericalDetectorItem.h
index 5011874138a40bd07f3068a3af908855ba9d3a0b..5168c1c640660428b5dc388ff04393ffc568e7c9 100644
--- a/GUI/Session/SphericalDetectorItem.h
+++ b/GUI/Items/SphericalDetectorItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/SphericalDetectorItem.h
+//! @file      GUI/Items/SphericalDetectorItem.h
 //! @brief     Defines class SphericalDetectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_SPHERICALDETECTORITEM_H
-#define BORNAGAIN_GUI_SESSION_SPHERICALDETECTORITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_SPHERICALDETECTORITEM_H
+#define BORNAGAIN_GUI_ITEMS_SPHERICALDETECTORITEM_H
 
-#include "GUI/Session/DetectorItems.h"
+#include "GUI/Items/DetectorItems.h"
 
 class BasicAxisItem;
 
@@ -45,4 +45,4 @@ protected:
     double axesToDomainUnitsFactor() const override;
 };
 
-#endif // BORNAGAIN_GUI_SESSION_SPHERICALDETECTORITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_SPHERICALDETECTORITEM_H
diff --git a/GUI/Session/TransformationItem.cpp b/GUI/Items/TransformationItem.cpp
similarity index 90%
rename from GUI/Session/TransformationItem.cpp
rename to GUI/Items/TransformationItem.cpp
index 4dbe26ab64d536f1c234b1ba3b108a51d37e2121..7b64e483d06a0030307e58fdde0c4b704f289405 100644
--- a/GUI/Session/TransformationItem.cpp
+++ b/GUI/Items/TransformationItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/TransformationItem.cpp
+//! @file      GUI/Items/TransformationItem.cpp
 //! @brief     Implements class TransformationItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,9 +12,9 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/TransformationItem.h"
+#include "GUI/Items/TransformationItem.h"
 #include "GUI/Models/Group/GroupInfo.h"
-#include "GUI/Session/RotationItems.h"
+#include "GUI/Items/RotationItems.h"
 
 TransformationItem::TransformationItem() : SessionGraphicsItem(M_TYPE)
 {
diff --git a/GUI/Session/TransformationItem.h b/GUI/Items/TransformationItem.h
similarity index 82%
rename from GUI/Session/TransformationItem.h
rename to GUI/Items/TransformationItem.h
index bbe9c8cbd794176971fc3dab5776d2f6ef5c9eb2..72d2be982103e8803062c1321704005647b4746a 100644
--- a/GUI/Session/TransformationItem.h
+++ b/GUI/Items/TransformationItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/TransformationItem.h
+//! @file      GUI/Items/TransformationItem.h
 //! @brief     Defines class TransformationItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,10 +12,10 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_TRANSFORMATIONITEM_H
-#define BORNAGAIN_GUI_SESSION_TRANSFORMATIONITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_TRANSFORMATIONITEM_H
+#define BORNAGAIN_GUI_ITEMS_TRANSFORMATIONITEM_H
 
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 
 class RotationItem;
 
@@ -42,4 +42,4 @@ template <typename T> T* TransformationItem::setRotationType()
     return setGroupPropertyType<T>(P_ROT);
 }
 
-#endif // BORNAGAIN_GUI_SESSION_TRANSFORMATIONITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_TRANSFORMATIONITEM_H
diff --git a/GUI/Session/VectorItem.cpp b/GUI/Items/VectorItem.cpp
similarity index 96%
rename from GUI/Session/VectorItem.cpp
rename to GUI/Items/VectorItem.cpp
index 2b64730456e45bd6ce933ce9ab3792b90a7dc737..54a588189fabced62d7586bdf16031625de40bc4 100644
--- a/GUI/Session/VectorItem.cpp
+++ b/GUI/Items/VectorItem.cpp
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/VectorItem.cpp
+//! @file      GUI/Items/VectorItem.cpp
 //! @brief     Implements class VectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 VectorItem::VectorItem() : SessionItem(M_TYPE)
 {
diff --git a/GUI/Session/VectorItem.h b/GUI/Items/VectorItem.h
similarity index 85%
rename from GUI/Session/VectorItem.h
rename to GUI/Items/VectorItem.h
index 04cc0481178a27339db6b050ac058f722286caec..eea3d75bbf81652c5d47af6e0cf85c7ae313fd3d 100644
--- a/GUI/Session/VectorItem.h
+++ b/GUI/Items/VectorItem.h
@@ -2,7 +2,7 @@
 //
 //  BornAgain: simulate and fit reflection and scattering
 //
-//! @file      GUI/Session/VectorItem.h
+//! @file      GUI/Items/VectorItem.h
 //! @brief     Defines class VectorItem
 //!
 //! @homepage  http://www.bornagainproject.org
@@ -12,11 +12,11 @@
 //
 //  ************************************************************************************************
 
-#ifndef BORNAGAIN_GUI_SESSION_VECTORITEM_H
-#define BORNAGAIN_GUI_SESSION_VECTORITEM_H
+#ifndef BORNAGAIN_GUI_ITEMS_VECTORITEM_H
+#define BORNAGAIN_GUI_ITEMS_VECTORITEM_H
 
 #include "Base/Vector/Vectors3D.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class BA_CORE_API_ VectorItem : public SessionItem {
 private:
@@ -50,4 +50,4 @@ private:
     void updateLabel();
 };
 
-#endif // BORNAGAIN_GUI_SESSION_VECTORITEM_H
+#endif // BORNAGAIN_GUI_ITEMS_VECTORITEM_H
diff --git a/GUI/Mapper/ComponentProxyModel.cpp b/GUI/Mapper/ComponentProxyModel.cpp
index 3655e839c1829dee131c7ad1e3ad534270df3b84..c9320eb999aaa0afcd0fd4c006a556d23d920947 100644
--- a/GUI/Mapper/ComponentProxyModel.cpp
+++ b/GUI/Mapper/ComponentProxyModel.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Mapper/ComponentProxyModel.h"
 #include "GUI/Mapper/ComponentProxyStrategy.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/SessionModel.h"
 #include <QSet>
 #include <functional>
 
diff --git a/GUI/Mapper/ComponentProxyStrategy.cpp b/GUI/Mapper/ComponentProxyStrategy.cpp
index f35d4bb7c2c8ae9cc8797dfa882ef5f00df87274..9b265b0ed3b2ae8ee885aea1a1754356ac23c64d 100644
--- a/GUI/Mapper/ComponentProxyStrategy.cpp
+++ b/GUI/Mapper/ComponentProxyStrategy.cpp
@@ -15,9 +15,9 @@
 #include "GUI/Mapper/ComponentProxyStrategy.h"
 #include "GUI/Mapper/ComponentProxyModel.h"
 #include "GUI/Mapper/ComponentUtils.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/SessionModel.h"
 
 void ComponentProxyStrategy::onDataChanged(SessionModel* source, ComponentProxyModel* proxy)
 {
diff --git a/GUI/Mapper/ComponentUtils.cpp b/GUI/Mapper/ComponentUtils.cpp
index d37e60d4a28e06d879e3193c4b4676af2a2f626a..7d29429690321b5298aa5d820ac2b9c5b5deb61c 100644
--- a/GUI/Mapper/ComponentUtils.cpp
+++ b/GUI/Mapper/ComponentUtils.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Mapper/ComponentUtils.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/MaterialDataItems.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/MaterialDataItems.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/VectorItem.h"
 
 namespace {
 QList<const SessionItem*> groupItems(const GroupItem& item);
diff --git a/GUI/Mapper/ModelMapper.cpp b/GUI/Mapper/ModelMapper.cpp
index 40c8ded04b6600f9c2bf49f85a3e924fc12b3d40..daa18477eb143acd54824b81631159e91b03c500 100644
--- a/GUI/Mapper/ModelMapper.cpp
+++ b/GUI/Mapper/ModelMapper.cpp
@@ -12,7 +12,7 @@
 //
 //  ************************************************************************************************
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 ModelMapper::ModelMapper(QObject* parent)
     : QObject(parent), m_active(true), m_model(nullptr), m_item(nullptr)
diff --git a/GUI/Mapper/ModelUtils.cpp b/GUI/Mapper/ModelUtils.cpp
index cc69253cf9a0c78b0b4bae245a23d200e0c8734b..824416b29f185024db58c35f5e605ec58f90c54f 100644
--- a/GUI/Mapper/ModelUtils.cpp
+++ b/GUI/Mapper/ModelUtils.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include <QAbstractItemModel>
 #include <QModelIndex>
 
diff --git a/GUI/Mapper/ProxyModelStrategy.cpp b/GUI/Mapper/ProxyModelStrategy.cpp
index b2218b40dd1b10b4bf88bc684cb87e2de0cca547..59bdd6ec830f2c93f6b445c63f5ce1e41fa170cb 100644
--- a/GUI/Mapper/ProxyModelStrategy.cpp
+++ b/GUI/Mapper/ProxyModelStrategy.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Mapper/ComponentProxyModel.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 ProxyModelStrategy::ProxyModelStrategy() : m_source(nullptr), m_proxy(nullptr) {}
 
diff --git a/GUI/Models/Data/ApplicationModels.cpp b/GUI/Models/Data/ApplicationModels.cpp
index e0325c6c4eb204bac620be515bbdbfe2623cbbdd..da4fbf530046c81d5ccdd7519b6b99bbe81dbc79 100644
--- a/GUI/Models/Data/ApplicationModels.cpp
+++ b/GUI/Models/Data/ApplicationModels.cpp
@@ -14,13 +14,13 @@
 
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/Models/Data/DocumentModel.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "GUI/utils/DeserializationException.h"
 #include <QtCore/QXmlStreamWriter>
 
diff --git a/GUI/Models/Data/DataProperties.cpp b/GUI/Models/Data/DataProperties.cpp
index 3c09bcc6adcba415b59a63afa6ea33f303f057bb..6529e75047faa82282511c1eb9eee059bcce76ed 100644
--- a/GUI/Models/Data/DataProperties.cpp
+++ b/GUI/Models/Data/DataProperties.cpp
@@ -14,10 +14,10 @@
 
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/SessionModel.h"
 #include <QColor>
 
 namespace {
diff --git a/GUI/Models/Data/DataProperties.h b/GUI/Models/Data/DataProperties.h
index f3385d75a21384b808dc078b45d09d452c81ccab..6d2f9727b6766d7250c692668f9d6b119d17eb48 100644
--- a/GUI/Models/Data/DataProperties.h
+++ b/GUI/Models/Data/DataProperties.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_DATA_DATAPROPERTIES_H
 #define BORNAGAIN_GUI_MODELS_DATA_DATAPROPERTIES_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class DataItem;
 
diff --git a/GUI/Models/Data/DataPropertyContainer.cpp b/GUI/Models/Data/DataPropertyContainer.cpp
index eaf7b87066d0654fffe914f324571e1767bd40e0..1823914fbfdc700d32c7fdca8374df27cb9d2650 100644
--- a/GUI/Models/Data/DataPropertyContainer.cpp
+++ b/GUI/Models/Data/DataPropertyContainer.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Data/DataPropertyContainer.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/utils/Error.h"
 
diff --git a/GUI/Models/Data/DataPropertyContainer.h b/GUI/Models/Data/DataPropertyContainer.h
index 311f3a39ab71cc414bacf86dd23480be4daeee23..27be65d563a035ba07fd94ecc02aef3fd4850659 100644
--- a/GUI/Models/Data/DataPropertyContainer.h
+++ b/GUI/Models/Data/DataPropertyContainer.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_DATA_DATAPROPERTYCONTAINER_H
 #define BORNAGAIN_GUI_MODELS_DATA_DATAPROPERTYCONTAINER_H
 
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 class DataItem;
 class DataProperties;
diff --git a/GUI/Models/Data/DataViewUtils.cpp b/GUI/Models/Data/DataViewUtils.cpp
index 68c90c3c3775808fec056041c53c58957993c040..5de3a31239ae587f6c9e63d4b45580ba54163ab5 100644
--- a/GUI/Models/Data/DataViewUtils.cpp
+++ b/GUI/Models/Data/DataViewUtils.cpp
@@ -14,11 +14,11 @@
 
 #include "GUI/Models/Data/DataViewUtils.h"
 #include "Device/Coord/ICoordSystem.h"
-#include "GUI/Session/Data1DViewItem.h"
-#include "GUI/Session/DataItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobItemUtils.h"
+#include "GUI/Items/Data1DViewItem.h"
+#include "GUI/Items/DataItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobItemUtils.h"
 
 namespace {
 
diff --git a/GUI/Models/Data/DocumentModel.cpp b/GUI/Models/Data/DocumentModel.cpp
index 9f6db5731d7b7563c2c1a1489c524e9ad2a9e72a..5d3a0a0d7fc9bb588b4758169abf7e2dc5bf8ca8 100644
--- a/GUI/Models/Data/DocumentModel.cpp
+++ b/GUI/Models/Data/DocumentModel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Data/DocumentModel.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 
 DocumentModel::DocumentModel(QObject* parent)
     : SessionModel(GUI::Session::XML::DocumentModelTag, parent)
diff --git a/GUI/Models/Data/DocumentModel.h b/GUI/Models/Data/DocumentModel.h
index 2fc013d4423757cb8538deea7cb3bb2c315292d1..88d03099ed27c9ec111e73b069ad4ef67ff1124f 100644
--- a/GUI/Models/Data/DocumentModel.h
+++ b/GUI/Models/Data/DocumentModel.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_DATA_DOCUMENTMODEL_H
 #define BORNAGAIN_GUI_MODELS_DATA_DOCUMENTMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 class SimulationOptionsItem;
 
diff --git a/GUI/Models/Data/GUIObjectBuilder.cpp b/GUI/Models/Data/GUIObjectBuilder.cpp
index b084fcf582d5c57a59d01d2084c62c32e5dacbd6..0ce935fed20e846deb5439ca2d3a0f2037af836f 100644
--- a/GUI/Models/Data/GUIObjectBuilder.cpp
+++ b/GUI/Models/Data/GUIObjectBuilder.cpp
@@ -19,9 +19,9 @@
 #include "Device/Instrument/Instrument.h"
 #include "GUI/Models/Data/DocumentModel.h"
 #include "GUI/Models/Sample/GUIDomainSampleVisitor.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "GUI/Models/Domain/TransformFromDomain.h"
 #include "Resample/Options/SimulationOptions.h"
 
diff --git a/GUI/Models/Data/ImportDataInfo.cpp b/GUI/Models/Data/ImportDataInfo.cpp
index a4d47e716d41d7a67cce640f0abe2580bf3d5650..b0a1c3db6c86c9c89b63b08bfa2242189e27fc5c 100644
--- a/GUI/Models/Data/ImportDataInfo.cpp
+++ b/GUI/Models/Data/ImportDataInfo.cpp
@@ -16,7 +16,7 @@
 #include "Device/Coord/AxisNames.h"
 #include "Device/Data/OutputData.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/JobItemUtils.h"
+#include "GUI/Items/JobItemUtils.h"
 #include "GUI/utils/OutputDataUtils.h"
 
 namespace {
diff --git a/GUI/Models/Data/MaskUnitsConverter.cpp b/GUI/Models/Data/MaskUnitsConverter.cpp
index 0d8adc905633095bf4654ee10e097e6ef9923400..6c1c4cbdd6ae8741e5f2abb7c363b0858f021607 100644
--- a/GUI/Models/Data/MaskUnitsConverter.cpp
+++ b/GUI/Models/Data/MaskUnitsConverter.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Models/Data/MaskUnitsConverter.h"
 #include "Device/Data/DataUtils.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
 
 #include <boost/polymorphic_cast.hpp>
 using boost::polymorphic_downcast;
diff --git a/GUI/Models/Data/RealDataModel.cpp b/GUI/Models/Data/RealDataModel.cpp
index 61e374a05af2e6e2400199f661c55a7bab25fc90..e4f3e4244b0036ae5f499de25cee8c853c5de658 100644
--- a/GUI/Models/Data/RealDataModel.cpp
+++ b/GUI/Models/Data/RealDataModel.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Data/RealDataModel.h"
-#include "GUI/Session/DataItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/DataItem.h"
+#include "GUI/Items/RealDataItem.h"
 
 RealDataModel::RealDataModel(QObject* parent)
     : SessionModel(GUI::Session::XML::RealDataModelTag, parent)
diff --git a/GUI/Models/Data/RealDataModel.h b/GUI/Models/Data/RealDataModel.h
index 188db5ffe4dc8cbb92f0542eb57f02354a7a5862..b8a07d0260f93131d9f15354b9c7b1f69604304d 100644
--- a/GUI/Models/Data/RealDataModel.h
+++ b/GUI/Models/Data/RealDataModel.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_DATA_REALDATAMODEL_H
 #define BORNAGAIN_GUI_MODELS_DATA_REALDATAMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 class RealDataItem;
 
diff --git a/GUI/Models/Domain/DomainObjectBuilder.cpp b/GUI/Models/Domain/DomainObjectBuilder.cpp
index cde80cc4d568d84848d43af5494c1ad60fc1f131..65c07c4420cd95e16e5f40b0c73a1565fad9cc29 100644
--- a/GUI/Models/Domain/DomainObjectBuilder.cpp
+++ b/GUI/Models/Domain/DomainObjectBuilder.cpp
@@ -14,11 +14,11 @@
 
 #include "GUI/Models/Domain/DomainObjectBuilder.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
 
 std::unique_ptr<MultiLayer>
diff --git a/GUI/Models/Domain/DomainSimulationBuilder.cpp b/GUI/Models/Domain/DomainSimulationBuilder.cpp
index b61f243bf0df1a46531e88e86b8974ed01c365e4..4945e2b09386ceeaedf8f5de7f039736aedc6172 100644
--- a/GUI/Models/Domain/DomainSimulationBuilder.cpp
+++ b/GUI/Models/Domain/DomainSimulationBuilder.cpp
@@ -19,14 +19,14 @@
 #include "Core/Simulation/includeSimulations.h"
 #include "Device/Beam/Beam.h"
 #include "Device/Beam/IFootprintFactor.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/BackgroundItems.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/BackgroundItems.h"
 #include "GUI/Models/Domain/DomainObjectBuilder.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FootprintItems.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/FootprintItems.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
 
 namespace {
diff --git a/GUI/Models/Domain/TransformFromDomain.cpp b/GUI/Models/Domain/TransformFromDomain.cpp
index e5f3f6227ba09f93b7b769127aacd7246d0f6102..00b4cc9cb68e693a4680ecce02062461aa6acf19 100644
--- a/GUI/Models/Domain/TransformFromDomain.cpp
+++ b/GUI/Models/Domain/TransformFromDomain.cpp
@@ -32,25 +32,25 @@
 #include "Device/Resolution/ConvolutionDetectorResolution.h"
 #include "Device/Resolution/ResolutionFunction2DGaussian.h"
 #include "Device/Resolution/ScanResolution.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/BackgroundItems.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/BackgroundItems.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FTDecayFunctionItems.h"
-#include "GUI/Session/FTDistributionItems.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/Lattice2DItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/ResolutionFunctionItems.h"
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/FTDecayFunctionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/Lattice2DItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 #include "GUI/Models/Types/UIntDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Param/Distrib/Distributions.h"
 #include "Param/Distrib/RangedDistributions.h"
 #include "Param/Node/NodeUtils.h"
diff --git a/GUI/Models/Domain/TransformToDomain.cpp b/GUI/Models/Domain/TransformToDomain.cpp
index 9ba2aefa0ef16b803dd5c9f05a95f27b3ce3e3e5..00b3fad786d80f0d85beab91f2b2c4b8a8886155 100644
--- a/GUI/Models/Domain/TransformToDomain.cpp
+++ b/GUI/Models/Domain/TransformToDomain.cpp
@@ -17,26 +17,26 @@
 #include "Core/Scan/AlphaScan.h"
 #include "Core/Simulation/GISASSimulation.h"
 #include "Device/Resolution/ScanResolution.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobModelFunctions.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MaterialItemUtils.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/RotationItems.h"
-#include "GUI/Session/SimulationOptionsItem.h"
-#include "GUI/Session/TransformationItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobModelFunctions.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MaterialItemUtils.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/RotationItems.h"
+#include "GUI/Items/SimulationOptionsItem.h"
+#include "GUI/Items/TransformationItem.h"
 #include "GUI/Models/Types/UIntDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Param/Distrib/RangedDistributions.h"
 #include "Resample/Options/SimulationOptions.h"
 #include "Sample/Particle/MesoCrystal.h"
diff --git a/GUI/Models/Fit/FitParameterProxyModel.cpp b/GUI/Models/Fit/FitParameterProxyModel.cpp
index bad0ea5beab5382130b05c4d5b07eb2637505fa0..87c85c808b5c3db79e5ad83c5a7a5670fe2e53d0 100644
--- a/GUI/Models/Fit/FitParameterProxyModel.cpp
+++ b/GUI/Models/Fit/FitParameterProxyModel.cpp
@@ -15,10 +15,10 @@
 #include "GUI/Models/Fit/FitParameterProxyModel.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Job/FitParameterHelper.h"
-#include "GUI/Session/FitParameterItems.h"
+#include "GUI/Items/FitParameterItems.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include <QColor>
 #include <QMimeData>
 
diff --git a/GUI/Models/Group/GroupInfo.h b/GUI/Models/Group/GroupInfo.h
index 77e74cd5248d9d7859979237b496f5e429f9f113..3b7a00c23a00b745146dab3889e6213de391cd09 100644
--- a/GUI/Models/Group/GroupInfo.h
+++ b/GUI/Models/Group/GroupInfo.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_GROUP_GROUPINFO_H
 #define BORNAGAIN_GUI_MODELS_GROUP_GROUPINFO_H
 
-#include "GUI/Session/ItemCatalog.h"
+#include "GUI/Items/ItemCatalog.h"
 #include <QString>
 #include <QStringList>
 #include <QVector>
diff --git a/GUI/Models/Group/SelectionDescriptor.h b/GUI/Models/Group/SelectionDescriptor.h
index b3001801e4abd08f8849d4788225b632b20697db..e111ecbdb07cad62bb8d5e45fb7c592222309950 100644
--- a/GUI/Models/Group/SelectionDescriptor.h
+++ b/GUI/Models/Group/SelectionDescriptor.h
@@ -16,7 +16,7 @@
 #define BORNAGAIN_GUI_MODELS_GROUP_SELECTIONDESCRIPTOR_H
 
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/GroupItem.h"
+#include "GUI/Items/GroupItem.h"
 #include <QString>
 #include <QStringList>
 #include <functional>
diff --git a/GUI/Models/Instrument/InstrumentLibrary.cpp b/GUI/Models/Instrument/InstrumentLibrary.cpp
index 7a8e93d07521c120c69d701970a96795380c5986..307d839b6f34e282cd27cce0b9eb2607aa89cbab 100644
--- a/GUI/Models/Instrument/InstrumentLibrary.cpp
+++ b/GUI/Models/Instrument/InstrumentLibrary.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Models/Instrument/InstrumentLibrary.h"
 #include "GUI/Models/Instrument/InstrumentsTreeModel.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include <QFile>
 #include <QXmlStreamWriter>
 
diff --git a/GUI/Models/Instrument/InstrumentModel.cpp b/GUI/Models/Instrument/InstrumentModel.cpp
index 8cbbddb35a27ee483aa95a342b2888405bd933bf..6ff6de5258b397406eebe5c05be706f2e5a31b9f 100644
--- a/GUI/Models/Instrument/InstrumentModel.cpp
+++ b/GUI/Models/Instrument/InstrumentModel.cpp
@@ -13,10 +13,10 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/PointwiseAxisItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
 
 InstrumentModel::InstrumentModel(QObject* parent)
     : SessionModel(GUI::Session::XML::InstrumentModelTag, parent)
diff --git a/GUI/Models/Instrument/InstrumentModel.h b/GUI/Models/Instrument/InstrumentModel.h
index 19e2761b7131e4eba7d91db37b846b67b7061c23..f09d4ff3125a5cae45895ae26f38b704b6474f2f 100644
--- a/GUI/Models/Instrument/InstrumentModel.h
+++ b/GUI/Models/Instrument/InstrumentModel.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_INSTRUMENT_INSTRUMENTMODEL_H
 #define BORNAGAIN_GUI_MODELS_INSTRUMENT_INSTRUMENTMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include <functional>
 
 class InstrumentItem;
diff --git a/GUI/Models/Instrument/InstrumentsTreeModel.cpp b/GUI/Models/Instrument/InstrumentsTreeModel.cpp
index e16e1fcae2337de49f857e6b54436593c7a1c672..80907274ea61a7a11b2a685cbdc0fa46958fbbb6 100644
--- a/GUI/Models/Instrument/InstrumentsTreeModel.cpp
+++ b/GUI/Models/Instrument/InstrumentsTreeModel.cpp
@@ -15,7 +15,7 @@
 #include "GUI/Models/Instrument/InstrumentsTreeModel.h"
 #include "GUI/Application/Application.h"
 #include "GUI/Application/ApplicationSettings.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include <QApplication>
 #include <QtCore>
diff --git a/GUI/Models/Job/FitParameterHelper.cpp b/GUI/Models/Job/FitParameterHelper.cpp
index fba2ac64c670b303ed3d6c8c7e3a3baf97b36083..5752642146e3bef1157dc1a10c9d4ca70c0e1436 100644
--- a/GUI/Models/Job/FitParameterHelper.cpp
+++ b/GUI/Models/Job/FitParameterHelper.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Job/FitParameterHelper.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/ParameterTreeItems.h"
 
 //! Creates fit parameter from given ParameterItem, sets starting value to the value
 //! of ParameterItem, copies link.
diff --git a/GUI/Models/Job/JobModel.cpp b/GUI/Models/Job/JobModel.cpp
index 6bd32e32b2ff602f6ec5a174c33244c4cc7df900..6310fb085631086fc3d0cb269d9099e71e0e18fd 100644
--- a/GUI/Models/Job/JobModel.cpp
+++ b/GUI/Models/Job/JobModel.cpp
@@ -13,17 +13,17 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobModelFunctions.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobModelFunctions.h"
 #include "GUI/Models/Job/JobQueueData.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include "GUI/Models/Job/ParameterTreeUtils.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/utils/Helpers.h"
 
 JobModel::JobModel(QObject* parent)
diff --git a/GUI/Models/Job/JobModel.h b/GUI/Models/Job/JobModel.h
index 2d9d7d1dbdf6ebd7c7a33eccd826322ae1af1526..3a7730cd9269a42cc2be58f6c44f6cbb6095e493 100644
--- a/GUI/Models/Job/JobModel.h
+++ b/GUI/Models/Job/JobModel.h
@@ -14,7 +14,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_JOB_JOBMODEL_H
 #define BORNAGAIN_GUI_MODELS_JOB_JOBMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 class JobQueueData;
 class JobItem;
 class MultiLayerItem;
diff --git a/GUI/Models/Job/JobQueueData.cpp b/GUI/Models/Job/JobQueueData.cpp
index 21f3e59748b6b1e9247fe5df0966dc6ed1e09b1e..a9a100b3fdcea81fd15ce3768b987213d06a70f4 100644
--- a/GUI/Models/Job/JobQueueData.cpp
+++ b/GUI/Models/Job/JobQueueData.cpp
@@ -16,7 +16,7 @@
 #include "Core/Simulation/GISASSimulation.h"
 #include "GUI/Models/Domain/DomainSimulationBuilder.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/Models/Job/JobWorker.h"
 #include "GUI/utils/Helpers.h"
diff --git a/GUI/Models/Job/ParameterTreeUtils.cpp b/GUI/Models/Job/ParameterTreeUtils.cpp
index d401780ca68c33603ce1f72bda72096dcf5cad97..ece7a649a2d2fe71d49dbefde5c1f6b0efbe0e77 100644
--- a/GUI/Models/Job/ParameterTreeUtils.cpp
+++ b/GUI/Models/Job/ParameterTreeUtils.cpp
@@ -14,14 +14,14 @@
 
 #include "GUI/Models/Job/ParameterTreeUtils.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/MaterialItemContainer.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParameterTreeItems.h"
-#include "GUI/Session/PropertyItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/MaterialItemContainer.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParameterTreeItems.h"
+#include "GUI/Items/PropertyItem.h"
 #include <QStack>
 
 #include <boost/polymorphic_cast.hpp>
diff --git a/GUI/Models/Material/MaterialModel.cpp b/GUI/Models/Material/MaterialModel.cpp
index bf607b70fdce5d317ee0181a4d8c79e91cd42a45..ebdba485f6b9a6c81d2a9b635d10e395135fb788 100644
--- a/GUI/Models/Material/MaterialModel.cpp
+++ b/GUI/Models/Material/MaterialModel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Material/MaterialModel.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Models/Material/MaterialModelStore.h"
 #include "GUI/utils/Helpers.h"
 
diff --git a/GUI/Models/Material/MaterialModel.h b/GUI/Models/Material/MaterialModel.h
index 20a834a46c24c0cfd708a9d1a16483319e875d68..3e905a5fd992e8ed0b8e51b8e6e95767db226602 100644
--- a/GUI/Models/Material/MaterialModel.h
+++ b/GUI/Models/Material/MaterialModel.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_MATERIAL_MATERIALMODEL_H
 #define BORNAGAIN_GUI_MODELS_MATERIAL_MATERIALMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 class MaterialItem;
 
diff --git a/GUI/Models/Parameter/FilterPropertyProxy.cpp b/GUI/Models/Parameter/FilterPropertyProxy.cpp
index 57f7f711d23d982913f15ee3d72494ef7ea4e259..f90c65b575ff1260f56ae8953afecc736436e3c4 100644
--- a/GUI/Models/Parameter/FilterPropertyProxy.cpp
+++ b/GUI/Models/Parameter/FilterPropertyProxy.cpp
@@ -13,10 +13,10 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 
 int FilterPropertyProxy::columnCount(const QModelIndex& parent) const
 {
diff --git a/GUI/Models/Parameter/ParameterTuningModel.cpp b/GUI/Models/Parameter/ParameterTuningModel.cpp
index 0ca7fe22bf2865036511dd72c4425bac8f9bd897..ad73ed7228af4c988019eee4f0227ded1a883373 100644
--- a/GUI/Models/Parameter/ParameterTuningModel.cpp
+++ b/GUI/Models/Parameter/ParameterTuningModel.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Models/Parameter/ParameterTuningModel.h"
 #include "GUI/Models/Job/FitParameterHelper.h"
-#include "GUI/Session/ParameterTreeItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/ParameterTreeItems.h"
+#include "GUI/Items/SessionModel.h"
 #include <QMimeData>
 
 ParameterTuningModel::ParameterTuningModel(QObject* parent) : FilterPropertyProxy(2, parent) {}
diff --git a/GUI/Models/Sample/GUIDomainSampleVisitor.cpp b/GUI/Models/Sample/GUIDomainSampleVisitor.cpp
index 170937f28f1a3273b1e64b1568bd4293f8465705..683526cb93b82fd7303e2a7f5c67ac0b06eb5607 100644
--- a/GUI/Models/Sample/GUIDomainSampleVisitor.cpp
+++ b/GUI/Models/Sample/GUIDomainSampleVisitor.cpp
@@ -17,22 +17,22 @@
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Models/Material/MaterialModel.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/RotationItems.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/RotationItems.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Models/Domain/TransformFromDomain.h"
-#include "GUI/Session/TransformationItem.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/TransformationItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Param/Node/NodeUtils.h"
 #include "Sample/Aggregate/ParticleLayout.h"
 #include "Sample/HardParticle/HardParticles.h"
diff --git a/GUI/Models/Sample/SampleListModel.cpp b/GUI/Models/Sample/SampleListModel.cpp
index 5809823211d22d80a8e6d7113ad857da94ca2ca6..0091de368556f084b073a272641c113581bdd711 100644
--- a/GUI/Models/Sample/SampleListModel.cpp
+++ b/GUI/Models/Sample/SampleListModel.cpp
@@ -16,7 +16,7 @@
 #include "GUI/Application/Application.h"
 #include "GUI/Models/Sample/GUIExamplesFactory.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Project/projectmanager.h"
 #include <QApplication>
diff --git a/GUI/Models/Sample/SampleModel.cpp b/GUI/Models/Sample/SampleModel.cpp
index e2a156017621ffbce700a5490789b25b1bad7c1f..7d6b3613a635deaa17385c857752c5b7cceec5ca 100644
--- a/GUI/Models/Sample/SampleModel.cpp
+++ b/GUI/Models/Sample/SampleModel.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/PropertyItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/PropertyItem.h"
 #include <QApplication>
 #include <QFontMetrics>
 #include <QPixmap>
diff --git a/GUI/Models/Sample/SampleModel.h b/GUI/Models/Sample/SampleModel.h
index 0a6d9b8b21e2a6d77fca2846b40e7116cba79c69..54c770841b22b9baa27fe474b3f012a4109ece08 100644
--- a/GUI/Models/Sample/SampleModel.h
+++ b/GUI/Models/Sample/SampleModel.h
@@ -15,7 +15,7 @@
 #ifndef BORNAGAIN_GUI_MODELS_SAMPLE_SAMPLEMODEL_H
 #define BORNAGAIN_GUI_MODELS_SAMPLE_SAMPLEMODEL_H
 
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 
 class MultiLayerItem;
 class ItemWithMaterial;
diff --git a/GUI/Models/Sample/SampleValidator.cpp b/GUI/Models/Sample/SampleValidator.cpp
index 5cb9900071bb6e1ac71357941d2fd9ca617cc353..6ceb8403cd886b4389e914319ef7de4700f4d4eb 100644
--- a/GUI/Models/Sample/SampleValidator.cpp
+++ b/GUI/Models/Sample/SampleValidator.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Sample/SampleValidator.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 
 #include <boost/polymorphic_cast.hpp>
 using boost::polymorphic_cast;
diff --git a/GUI/Models/Types/DoubleDescriptor.cpp b/GUI/Models/Types/DoubleDescriptor.cpp
index 65f551929f34bcb79e4ed2ddc28ac494851e815a..aeed867834b3dfaef5e47c88d4ae589fbb39748f 100644
--- a/GUI/Models/Types/DoubleDescriptor.cpp
+++ b/GUI/Models/Types/DoubleDescriptor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/SessionItem.h"
 
 DoubleDescriptor::DoubleDescriptor(const QString& label, SessionItem* item,
                                    const variant<QString, Unit>& unit)
diff --git a/GUI/Models/Types/UIntDescriptor.cpp b/GUI/Models/Types/UIntDescriptor.cpp
index d530752d4a025d253ab5895f7f7b3094f292b2a7..07e7c0609d7fadae22b02d5668fdd98cadc1d152 100644
--- a/GUI/Models/Types/UIntDescriptor.cpp
+++ b/GUI/Models/Types/UIntDescriptor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Models/Types/UIntDescriptor.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 
 UIntDescriptor::UIntDescriptor(const QString& label, SessionItem* item,
                                const variant<QString, Unit>& unit)
diff --git a/GUI/Models/Types/VectorDescriptor.h b/GUI/Models/Types/VectorDescriptor.h
index ef5bca6a69044d84d70d30c210adf4f1c9ab7f5e..631096ac518a8ab698bbee5954d80ad21737d81d 100644
--- a/GUI/Models/Types/VectorDescriptor.h
+++ b/GUI/Models/Types/VectorDescriptor.h
@@ -16,7 +16,7 @@
 #define BORNAGAIN_GUI_MODELS_TYPES_VECTORDESCRIPTOR_H
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 //! Describes properties of a 3D vector, consisting of three double values.
 //!
diff --git a/GUI/Views/FitWidgets/FitActivityPanel.cpp b/GUI/Views/FitWidgets/FitActivityPanel.cpp
index 445f75893ff4c8a5b6818c78ee237a5256969c74..8418f5124ef6b36ff12f6f3faf0565ae033e232f 100644
--- a/GUI/Views/FitWidgets/FitActivityPanel.cpp
+++ b/GUI/Views/FitWidgets/FitActivityPanel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/FitActivityPanel.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/Views/FitWidgets/FitSessionController.h"
 #include "GUI/Views/FitWidgets/FitSessionManager.h"
diff --git a/GUI/Views/FitWidgets/FitObjectiveBuilder.cpp b/GUI/Views/FitWidgets/FitObjectiveBuilder.cpp
index 8a93cbcc8526723e163c00d876cadcc8160c6f76..07f0af1ab2a9a3425c6f756dec16674a4314791f 100644
--- a/GUI/Views/FitWidgets/FitObjectiveBuilder.cpp
+++ b/GUI/Views/FitWidgets/FitObjectiveBuilder.cpp
@@ -18,14 +18,14 @@
 #include "Core/Simulation/ISimulation.h"
 #include "Fit/Kernel/Minimizer.h"
 #include "Fit/Minimizer/IMinimizer.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Domain/DomainSimulationBuilder.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/MinimizerItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/MinimizerItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Views/FitWidgets/GUIFitObserver.h"
 #include "GUI/utils/Helpers.h"
 
diff --git a/GUI/Views/FitWidgets/FitParameterWidget.cpp b/GUI/Views/FitWidgets/FitParameterWidget.cpp
index d6637cd42ae38a0da9bfee843597e941fc36cb72..3e6e7df9b4a5a0b7c14c9aeb92f1fbe3456ae604 100644
--- a/GUI/Views/FitWidgets/FitParameterWidget.cpp
+++ b/GUI/Views/FitWidgets/FitParameterWidget.cpp
@@ -15,12 +15,12 @@
 #include "GUI/Views/FitWidgets/FitParameterWidget.h"
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
 #include "GUI/Models/Job/FitParameterHelper.h"
-#include "GUI/Session/FitParameterItems.h"
+#include "GUI/Items/FitParameterItems.h"
 #include "GUI/Models/Fit/FitParameterProxyModel.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include "GUI/Views/FitWidgets/ParameterTuningWidget.h"
 #include "GUI/InfoWidgets/OverlayLabelController.h"
 #include "GUI/Views/PropertyEditor/SessionModelDelegate.h"
diff --git a/GUI/Views/FitWidgets/FitSessionController.cpp b/GUI/Views/FitWidgets/FitSessionController.cpp
index 0fe13765c44a97887cc4a6ccda3ec21e15f59840..4d5c44295d5cc5b7605b6edc665f3b962459850c 100644
--- a/GUI/Views/FitWidgets/FitSessionController.cpp
+++ b/GUI/Views/FitWidgets/FitSessionController.cpp
@@ -14,10 +14,10 @@
 
 #include "GUI/Views/FitWidgets/FitSessionController.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FitParameterItems.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/FitParameterItems.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/FitWidgets/FitLog.h"
 #include "GUI/Views/FitWidgets/FitObjectiveBuilder.h"
 #include "GUI/Views/FitWidgets/FitWorkerLauncher.h"
diff --git a/GUI/Views/FitWidgets/FitSessionManager.cpp b/GUI/Views/FitWidgets/FitSessionManager.cpp
index 0c9aa90a765c90d4a58e6e397067c0f4081942e6..f598971c11c2096969b8f71b05a93faa57c36a50 100644
--- a/GUI/Views/FitWidgets/FitSessionManager.cpp
+++ b/GUI/Views/FitWidgets/FitSessionManager.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/FitWidgets/FitSessionManager.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/FitWidgets/FitLog.h"
 #include "GUI/Views/FitWidgets/FitSessionController.h"
 
diff --git a/GUI/Views/FitWidgets/FitSessionWidget.cpp b/GUI/Views/FitWidgets/FitSessionWidget.cpp
index cda3a3929c7b7b2eaf2b97bfeb93fef234e36b54..76654d09e05c20d9ce45229981dab53ae6c3d18b 100644
--- a/GUI/Views/FitWidgets/FitSessionWidget.cpp
+++ b/GUI/Views/FitWidgets/FitSessionWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/FitSessionWidget.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/FitWidgets/FitParameterWidget.h"
 #include "GUI/Views/FitWidgets/FitResultsWidget.h"
 #include "GUI/Views/FitWidgets/FitSessionController.h"
diff --git a/GUI/Views/FitWidgets/JobRealTimeWidget.cpp b/GUI/Views/FitWidgets/JobRealTimeWidget.cpp
index 799ca0adb96a56fb891e5cd2e325407c834cdaaf..95708b821d2bcd1653d2f9865404f598bf1e49b4 100644
--- a/GUI/Views/FitWidgets/JobRealTimeWidget.cpp
+++ b/GUI/Views/FitWidgets/JobRealTimeWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/JobRealTimeWidget.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/Views/FitWidgets/ParameterTuningWidget.h"
 #include "GUI/utils/mainwindow_constants.h"
diff --git a/GUI/Views/FitWidgets/MinimizerSettingsWidget.cpp b/GUI/Views/FitWidgets/MinimizerSettingsWidget.cpp
index e86f4c8271b6a33fd6aa3045896931a52fa0c586..a59d12f4e28704253bc6a3339bfee2223735cdc3 100644
--- a/GUI/Views/FitWidgets/MinimizerSettingsWidget.cpp
+++ b/GUI/Views/FitWidgets/MinimizerSettingsWidget.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/MinimizerSettingsWidget.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/MinimizerItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/MinimizerItem.h"
 #include "GUI/Views/PropertyEditor/ComponentEditor.h"
 #include <QPushButton>
 #include <QVBoxLayout>
diff --git a/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp b/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
index 62e629ee5435795a86d9deeffbce4561dae42d7f..cf36c4532e3908c96663ef863569ed28a2b6ba74 100644
--- a/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
+++ b/GUI/Views/FitWidgets/ParameterTuningDelegate.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/ParameterTuningDelegate.h"
-#include "GUI/Session/ModelPath.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/ModelPath.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include "GUI/Models/Parameter/ParameterTuningModel.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/CommonWidgets/ScientificSpinBox.h"
 #include <QAbstractItemModel>
 #include <QApplication>
diff --git a/GUI/Views/FitWidgets/ParameterTuningWidget.cpp b/GUI/Views/FitWidgets/ParameterTuningWidget.cpp
index 8a0e532b292873aac2ca4cfd2f46e09686432d8a..3abc4fbaaaeedafe27ef8067690c22af36e0365a 100644
--- a/GUI/Views/FitWidgets/ParameterTuningWidget.cpp
+++ b/GUI/Views/FitWidgets/ParameterTuningWidget.cpp
@@ -14,10 +14,10 @@
 
 #include "GUI/Views/FitWidgets/ParameterTuningWidget.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/ParameterTreeItems.h"
+#include "GUI/Items/ParameterTreeItems.h"
 #include "GUI/Models/Parameter/ParameterTuningModel.h"
 #include "GUI/Views/FitWidgets/JobRealTimeToolBar.h"
 #include "GUI/Views/FitWidgets/ParameterTuningDelegate.h"
diff --git a/GUI/Views/FitWidgets/RunFitControlWidget.cpp b/GUI/Views/FitWidgets/RunFitControlWidget.cpp
index 36aa4a6c8492725ca3b12892891bbc700fc1f8a5..151e1d79ff56b2618760a151657e377ed0950558 100644
--- a/GUI/Views/FitWidgets/RunFitControlWidget.cpp
+++ b/GUI/Views/FitWidgets/RunFitControlWidget.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/FitWidgets/RunFitControlWidget.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/InfoWidgets/CautionSign.h"
 #include "GUI/utils/mainwindow_constants.h"
diff --git a/GUI/Views/ImportDataWidgets/ImportDataUtils.cpp b/GUI/Views/ImportDataWidgets/ImportDataUtils.cpp
index d0975f8adccb73ad90776ff4c0021529f7ba1c49..665b9f8b3ba3e654aae46ec2284c3a16c0be0c60 100644
--- a/GUI/Views/ImportDataWidgets/ImportDataUtils.cpp
+++ b/GUI/Views/ImportDataWidgets/ImportDataUtils.cpp
@@ -16,8 +16,8 @@
 #include "Device/Data/OutputData.h"
 #include "Device/InputOutput/DataFormatUtils.h"
 #include "GUI/DataLoaders/QREDataLoader.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/utils/OutputDataUtils.h"
 #include <QApplication>
 #include <QMessageBox>
diff --git a/GUI/Views/ImportDataWidgets/RealDataMaskWidget.cpp b/GUI/Views/ImportDataWidgets/RealDataMaskWidget.cpp
index bdd831a061b907a6276b27ad2d89d6c31058ed8c..e21454d90afaab59f4626bc7f8d6651f424cdfdf 100644
--- a/GUI/Views/ImportDataWidgets/RealDataMaskWidget.cpp
+++ b/GUI/Views/ImportDataWidgets/RealDataMaskWidget.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ImportDataWidgets/RealDataMaskWidget.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Views/MaskWidgets/MaskEditor.h"
 #include <QAction>
 #include <QBoxLayout>
diff --git a/GUI/Views/ImportDataWidgets/RealDataPresenter.cpp b/GUI/Views/ImportDataWidgets/RealDataPresenter.cpp
index 2abaf3f2ca2fa71e504f50a9154cd4f9e4fe1d08..8fdb991914bfbebe3f499ab425b586d82ffaecd3 100644
--- a/GUI/Views/ImportDataWidgets/RealDataPresenter.cpp
+++ b/GUI/Views/ImportDataWidgets/RealDataPresenter.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/ImportDataWidgets/RealDataPresenter.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Views/ImportDataWidgets/RealDataMaskWidget.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataWidget.h"
 #include "GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.h"
diff --git a/GUI/Views/ImportDataWidgets/RealDataPropertiesWidget.cpp b/GUI/Views/ImportDataWidgets/RealDataPropertiesWidget.cpp
index 1b1c784e6cfd8c3a53b0f36527ea882e99ce8162..4aaa1ce7f4326db4b0116fbdc08e67eb2eab0684 100644
--- a/GUI/Views/ImportDataWidgets/RealDataPropertiesWidget.cpp
+++ b/GUI/Views/ImportDataWidgets/RealDataPropertiesWidget.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ImportDataWidgets/RealDataPropertiesWidget.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/mainwindow/mainwindow.h"
 #include "GUI/Project/projectdocument.h"
 #include <QComboBox>
diff --git a/GUI/Views/ImportDataWidgets/RealDataSelectorWidget.cpp b/GUI/Views/ImportDataWidgets/RealDataSelectorWidget.cpp
index 726cfdd23c5d9a710cc138e3669f072855e25286..597ccfd56d4d8409dc6a47c7bc234bdb9063e67f 100644
--- a/GUI/Views/ImportDataWidgets/RealDataSelectorWidget.cpp
+++ b/GUI/Views/ImportDataWidgets/RealDataSelectorWidget.cpp
@@ -18,7 +18,7 @@
 #include "GUI/Models/Data/AbstractDataLoader1D.h"
 #include "GUI/Models/Data/DataLoaders1D.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/CommonWidgets/GUIHelpers.h"
 #include "GUI/CommonWidgets/ItemViewOverlayButtons.h"
diff --git a/GUI/Views/ImportDataWidgets/RealDataTreeModel.cpp b/GUI/Views/ImportDataWidgets/RealDataTreeModel.cpp
index 587781b09c3e2814d67aa51181061532f3cfa8da..a7e16b58d13bac7e9ae391d24d2997dcfb06b63f 100644
--- a/GUI/Views/ImportDataWidgets/RealDataTreeModel.cpp
+++ b/GUI/Views/ImportDataWidgets/RealDataTreeModel.cpp
@@ -15,7 +15,7 @@
 #include "GUI/Views/ImportDataWidgets/RealDataTreeModel.h"
 #include "GUI/Application/Application.h"
 #include "GUI/Application/ApplicationSettings.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include <QApplication>
 #include <QtCore>
diff --git a/GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.cpp b/GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.cpp
index 797f2e73833f271bae03ef5947e7fa81350729d7..f81237dcdae6f839ca6b2087722185a6442cfb4a 100644
--- a/GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.h"
-#include "GUI/Session/BeamWavelengthItem.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 #include "GUI/Views/InstrumentWidgets/InclinationAnglesEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.cpp b/GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.cpp
index 9b151f910139c8112eb96dec78a33506db0d5c59..b462530a1659f52d395f289c2f70c47063a6b780 100644
--- a/GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.h"
-#include "GUI/Session/RectangularDetectorItem.h"
+#include "GUI/Items/RectangularDetectorItem.h"
 #include "GUI/Views/InstrumentWidgets/VectorEditor.h"
 
 #include <QComboBox>
diff --git a/GUI/Views/InstrumentWidgets/DetectorEditor.cpp b/GUI/Views/InstrumentWidgets/DetectorEditor.cpp
index 5422a7b7a606174ffc50d7c05085753394f3d6fc..8ace3e5ee6d0f4d8152dbb11be68d7096023c9e0 100644
--- a/GUI/Views/InstrumentWidgets/DetectorEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/DetectorEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DetectorEditor.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 #include "GUI/Views/InstrumentWidgets/RectangularDetectorEditor.h"
 #include "GUI/Views/InstrumentWidgets/SphericalDetectorEditor.h"
 
diff --git a/GUI/Views/InstrumentWidgets/DistributionEditor.cpp b/GUI/Views/InstrumentWidgets/DistributionEditor.cpp
index 23d38fe668709e9c61e190f9d7c2839aebafc719..95fe9664f9ed07a7ad7020518b3e449fc451d374 100644
--- a/GUI/Views/InstrumentWidgets/DistributionEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/DistributionEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
-#include "GUI/Session/DistributionItems.h"
-#include "GUI/Session/ItemWithDistribution.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/DistributionItems.h"
+#include "GUI/Items/ItemWithDistribution.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/InstrumentWidgets/DistributionForms.h"
 #include "GUI/Views/InstrumentWidgets/EditDistributionDialog.h"
 #include "GUI/Views/PropertyEditor/GroupInfoBox.h"
diff --git a/GUI/Views/InstrumentWidgets/DistributionForms.cpp b/GUI/Views/InstrumentWidgets/DistributionForms.cpp
index 71c62d74a814391946a2d6d02e507d5bb89e8a35..0a41906d8574611c86913b940ca27af247e1457f 100644
--- a/GUI/Views/InstrumentWidgets/DistributionForms.cpp
+++ b/GUI/Views/InstrumentWidgets/DistributionForms.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DistributionForms.h"
-#include "GUI/Session/DistributionItems.h"
-#include "GUI/Session/ItemWithDistribution.h"
+#include "GUI/Items/DistributionItems.h"
+#include "GUI/Items/ItemWithDistribution.h"
 #include "GUI/CommonWidgets/ScientificSpinBox.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 
diff --git a/GUI/Views/InstrumentWidgets/DistributionPlot.cpp b/GUI/Views/InstrumentWidgets/DistributionPlot.cpp
index c514a3015ed5f3d502e02a0eeebbc4d8103eb4cf..11423a09a70c340ebb48035cf638eb8e932f74e5 100644
--- a/GUI/Views/InstrumentWidgets/DistributionPlot.cpp
+++ b/GUI/Views/InstrumentWidgets/DistributionPlot.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/DistributionPlot.h"
-#include "GUI/Session/DistributionItems.h"
-#include "GUI/Session/RealLimitsItems.h"
+#include "GUI/Items/DistributionItems.h"
+#include "GUI/Items/RealLimitsItems.h"
 #include "GUI/InfoWidgets/CautionSign.h"
 #include "Param/Distrib/Distributions.h"
 #include <QLabel>
diff --git a/GUI/Views/InstrumentWidgets/EditDistributionDialog.cpp b/GUI/Views/InstrumentWidgets/EditDistributionDialog.cpp
index 6b80eace16d52783af30981a47d7a653b33ce364..a96c9d6832fbf03bcc2817154d4d21aa51fda835 100644
--- a/GUI/Views/InstrumentWidgets/EditDistributionDialog.cpp
+++ b/GUI/Views/InstrumentWidgets/EditDistributionDialog.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/EditDistributionDialog.h"
-#include "GUI/Session/ItemWithDistribution.h"
+#include "GUI/Items/ItemWithDistribution.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 #include "GUI/Views/InstrumentWidgets/DistributionPlot.h"
 
diff --git a/GUI/Views/InstrumentWidgets/EnvironmentEditor.cpp b/GUI/Views/InstrumentWidgets/EnvironmentEditor.cpp
index 9a4cfd088b2c56e5b33e02e6a08d23b7a081fe7f..a7d50af0621dde743f992a0348ef6f90588a902a 100644
--- a/GUI/Views/InstrumentWidgets/EnvironmentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/EnvironmentEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/EnvironmentEditor.h"
-#include "GUI/Session/BackgroundItems.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/BackgroundItems.h"
+#include "GUI/Items/InstrumentItems.h"
 
 #include <QComboBox>
 #include <QDoubleSpinBox>
diff --git a/GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.cpp b/GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.cpp
index 8a556b34ed21811ed96707d600f4c249a709a058..dc05a9bacdf12fef486725513deb299048929b27 100644
--- a/GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.h"
-#include "GUI/Session/FootprintItems.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/FootprintItems.h"
+#include "GUI/Items/InstrumentItems.h"
 
 #include <QComboBox>
 #include <QDoubleSpinBox>
diff --git a/GUI/Views/InstrumentWidgets/GISASBeamEditor.cpp b/GUI/Views/InstrumentWidgets/GISASBeamEditor.cpp
index d508a00ecad19e5ad2603bf197f38efd4195018e..2be9180c9227f523738d49cc9f591780bf5aa39e 100644
--- a/GUI/Views/InstrumentWidgets/GISASBeamEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/GISASBeamEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/GISASBeamEditor.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 
 #include <QDoubleValidator>
diff --git a/GUI/Views/InstrumentWidgets/GISASInstrumentEditor.cpp b/GUI/Views/InstrumentWidgets/GISASInstrumentEditor.cpp
index 3425a5684437708d2488067145a578587510cea1..4b5565831da2e17ea433566f46a46a0b405d2365 100644
--- a/GUI/Views/InstrumentWidgets/GISASInstrumentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/GISASInstrumentEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/GISASInstrumentEditor.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/InstrumentWidgets/DetectorEditor.h"
 #include "GUI/Views/InstrumentWidgets/EnvironmentEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/InclinationAnglesEditor.cpp b/GUI/Views/InstrumentWidgets/InclinationAnglesEditor.cpp
index c7eecf59296e39b68ecc34ba9ebbf3843813600a..c7ea5de23646fdfcd4aacb144da9a2a4a1dc4a21 100644
--- a/GUI/Views/InstrumentWidgets/InclinationAnglesEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/InclinationAnglesEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/InclinationAnglesEditor.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/SpecularBeamInclinationItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/SpecularBeamInclinationItem.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 #include "GUI/Views/InstrumentWidgets/SphericalAxisEditor.h"
 #include "GUI/Views/PropertyEditor/GroupInfoBox.h"
diff --git a/GUI/Views/InstrumentWidgets/InstrumentEditor.cpp b/GUI/Views/InstrumentWidgets/InstrumentEditor.cpp
index b3431147fac1e0483267a65389ca98a460aaf3cc..a95e54e3ee698e51c0f18e25990aad922aba71a8 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentEditor.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/InstrumentWidgets/InstrumentEditor.h"
 #include "Base/Utils/Assert.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Views/InstrumentWidgets/DepthProbeInstrumentEditor.h"
 #include "GUI/Views/InstrumentWidgets/GISASInstrumentEditor.h"
 #include "GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.cpp b/GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.cpp
index 5d6e60d21a1174ffeb72514c3213ebec94feab06..9ce20171314d79335fe37648cf8bb1e7d4331dac 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.h"
 #include "GUI/Application/Application.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/CommonWidgets/ItemViewOverlayButtons.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/mainwindow/mainwindow.h"
diff --git a/GUI/Views/InstrumentWidgets/InstrumentListModel.cpp b/GUI/Views/InstrumentWidgets/InstrumentListModel.cpp
index 9d067dc4c362ff4cf3366f04f85e7364e4dcb575..11276e68d9f351350b71c4fa876583ba0ce63fa3 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentListModel.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentListModel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/InstrumentListModel.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 
 
diff --git a/GUI/Views/InstrumentWidgets/InstrumentListView.cpp b/GUI/Views/InstrumentWidgets/InstrumentListView.cpp
index 0d21d49aec1c217044118091b4a596736a9954b9..2e6374d48f7a3cc3ec8ca787596cae3739227f69 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentListView.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentListView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/InstrumentWidgets/InstrumentListView.h"
 #include "GUI/Application/Application.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include "GUI/Views/InstrumentWidgets/InstrumentLibraryEditor.h"
 #include "GUI/Views/InstrumentWidgets/InstrumentListModel.h"
diff --git a/GUI/Views/InstrumentWidgets/InstrumentView.cpp b/GUI/Views/InstrumentWidgets/InstrumentView.cpp
index 11909f351cf242b4a3ca90e20faa613a05138e4c..53ef53b1891c3ae694a4f6fb2933ce638885c367 100644
--- a/GUI/Views/InstrumentWidgets/InstrumentView.cpp
+++ b/GUI/Views/InstrumentWidgets/InstrumentView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/InstrumentView.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include "GUI/CommonWidgets/StyledToolBar.h"
 #include "GUI/Views/InstrumentWidgets/InstrumentEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.cpp b/GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.cpp
index 1691d1a4f1eec89347041de0c8d9dbc3b53b4d66..b072ef4957909b62c36f903ea52b7f34b2125e9a 100644
--- a/GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.h"
-#include "GUI/Session/BeamAngleItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/BeamAngleItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 #include "GUI/Views/InstrumentWidgets/SphericalAxisEditor.h"
 
diff --git a/GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.cpp b/GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.cpp
index 5c5d469d97e38d513312dc1a934b866217c094c6..6c2ca299ffca1c5318f5ec04f84bb65653985f08 100644
--- a/GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/OffSpecularInstrumentEditor.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/InstrumentWidgets/DetectorEditor.h"
 #include "GUI/Views/InstrumentWidgets/OffSpecularBeamEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.cpp b/GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.cpp
index b8a0b9cd49e4401d4b3fb4e3757d794509d3747d..e75ef90030f3f45db175ad372a11bdfde8d3a870 100644
--- a/GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.h"
-#include "GUI/Session/DetectorItems.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/DetectorItems.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/Views/InstrumentWidgets/VectorEditor.h"
 
 #include <QCheckBox>
diff --git a/GUI/Views/InstrumentWidgets/RectangularDetectorEditor.cpp b/GUI/Views/InstrumentWidgets/RectangularDetectorEditor.cpp
index 43d2dd63f5d2d83d889bb598e6c2b2264691f693..12bf3d3b10dad1c1194356ca3188b54b94b062f1 100644
--- a/GUI/Views/InstrumentWidgets/RectangularDetectorEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/RectangularDetectorEditor.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/RectangularDetectorEditor.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/Views/InstrumentWidgets/DetectorAlignmentEditor.h"
 #include "GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.h"
 
diff --git a/GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.cpp b/GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.cpp
index 1ca7ba59b188fc2aabae8813c392aa90aebe0bfc..fe7fe2f30c3f843f56f442f0184b4e4433b555e3 100644
--- a/GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.h"
-#include "GUI/Session/DetectorItems.h"
-#include "GUI/Session/ResolutionFunctionItems.h"
+#include "GUI/Items/DetectorItems.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
 
 #include <QComboBox>
 #include <QDoubleSpinBox>
diff --git a/GUI/Views/InstrumentWidgets/SpecularBeamEditor.cpp b/GUI/Views/InstrumentWidgets/SpecularBeamEditor.cpp
index edc756ebe1ec440fa6b498b8ada85d256292de1a..e75fbea112bae6b03d2ee30e9f22a45d5101f806 100644
--- a/GUI/Views/InstrumentWidgets/SpecularBeamEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/SpecularBeamEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/SpecularBeamEditor.h"
-#include "GUI/Session/BeamItems.h"
-#include "GUI/Session/BeamWavelengthItem.h"
+#include "GUI/Items/BeamItems.h"
+#include "GUI/Items/BeamWavelengthItem.h"
 #include "GUI/Views/InstrumentWidgets/DistributionEditor.h"
 #include "GUI/Views/InstrumentWidgets/FootprintCorrectionEditor.h"
 #include "GUI/Views/InstrumentWidgets/InclinationAnglesEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/SpecularInstrumentEditor.cpp b/GUI/Views/InstrumentWidgets/SpecularInstrumentEditor.cpp
index 77b55f671c2d68a5f2f20d681830b38c919cda79..b66f43eeb868cee3a5681de99ecba3b940f7c8bf 100644
--- a/GUI/Views/InstrumentWidgets/SpecularInstrumentEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/SpecularInstrumentEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/SpecularInstrumentEditor.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/InstrumentWidgets/EnvironmentEditor.h"
 #include "GUI/Views/InstrumentWidgets/PolarizationAnalysisEditor.h"
diff --git a/GUI/Views/InstrumentWidgets/SphericalAxisEditor.cpp b/GUI/Views/InstrumentWidgets/SphericalAxisEditor.cpp
index f4e7c19caf015e2284ee522b7192481473ca1c24..6fd56673e56ea1edaf7bdb72b34b25d9b7273482 100644
--- a/GUI/Views/InstrumentWidgets/SphericalAxisEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/SphericalAxisEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/SphericalAxisEditor.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 
 #include <QDoubleSpinBox>
 #include <QFormLayout>
diff --git a/GUI/Views/InstrumentWidgets/SphericalDetectorEditor.cpp b/GUI/Views/InstrumentWidgets/SphericalDetectorEditor.cpp
index b0d0473aeb2ce16bfb22b8333ae50dbbc7febb71..1d7912a29c502d611b2a1b24c90ce7f47dafeeb5 100644
--- a/GUI/Views/InstrumentWidgets/SphericalDetectorEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/SphericalDetectorEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/SphericalDetectorEditor.h"
-#include "GUI/Session/SphericalDetectorItem.h"
+#include "GUI/Items/SphericalDetectorItem.h"
 #include "GUI/Views/InstrumentWidgets/ResolutionFunctionEditor.h"
 #include "GUI/Views/InstrumentWidgets/SphericalAxisEditor.h"
 
diff --git a/GUI/Views/InstrumentWidgets/VectorEditor.cpp b/GUI/Views/InstrumentWidgets/VectorEditor.cpp
index ba18d86e3cbfffc67109ae9049e1a78a14df6d29..e6189930c94411357c6047b07d48c3ab7bf514bc 100644
--- a/GUI/Views/InstrumentWidgets/VectorEditor.cpp
+++ b/GUI/Views/InstrumentWidgets/VectorEditor.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/InstrumentWidgets/VectorEditor.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 
 #include <QDoubleSpinBox>
 #include <QFormLayout>
diff --git a/GUI/Views/IntensityDataWidgets/ColorMap.cpp b/GUI/Views/IntensityDataWidgets/ColorMap.cpp
index 701acda468c1d33adebf7c67f324bb10c2ca9045..189b6a0e9962034a4b8486f33627543f978a3d0b 100644
--- a/GUI/Views/IntensityDataWidgets/ColorMap.cpp
+++ b/GUI/Views/IntensityDataWidgets/ColorMap.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/CommonWidgets/UpdateTimer.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMapUtils.h"
 #include "GUI/Views/IntensityDataWidgets/PlotEventInfo.h"
diff --git a/GUI/Views/IntensityDataWidgets/ColorMapCanvas.cpp b/GUI/Views/IntensityDataWidgets/ColorMapCanvas.cpp
index b82d0c91364b23b5c0772392da509a2b3d69b764..f3c299d71d24c515ab690e53e16cf0dbf5cc3526 100644
--- a/GUI/Views/IntensityDataWidgets/ColorMapCanvas.cpp
+++ b/GUI/Views/IntensityDataWidgets/ColorMapCanvas.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/IntensityDataWidgets/ColorMapCanvas.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/IntensityDataWidgets/FontScalingEvent.h"
 #include "GUI/Views/IntensityDataWidgets/PlotStatusLabel.h"
diff --git a/GUI/Views/IntensityDataWidgets/ColorMapUtils.cpp b/GUI/Views/IntensityDataWidgets/ColorMapUtils.cpp
index b85f03904c2f1f95e0dd8b24eaca17126e78ac10..3d3bc385ce99c4c32ce6db9c225ca750ad945a6a 100644
--- a/GUI/Views/IntensityDataWidgets/ColorMapUtils.cpp
+++ b/GUI/Views/IntensityDataWidgets/ColorMapUtils.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/IntensityDataWidgets/ColorMapUtils.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 
 using gradient_map_t = QMap<QString, QCPColorGradient::GradientPreset>;
diff --git a/GUI/Views/IntensityDataWidgets/IntensityDataCanvas.cpp b/GUI/Views/IntensityDataWidgets/IntensityDataCanvas.cpp
index b97f7df663ad45ac9847633473132198f64dfd1d..d104e5d21010c81f831489bc20808fe16afeb267 100644
--- a/GUI/Views/IntensityDataWidgets/IntensityDataCanvas.cpp
+++ b/GUI/Views/IntensityDataWidgets/IntensityDataCanvas.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Views/IntensityDataWidgets/IntensityDataCanvas.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/CommonWidgets/GUIHelpers.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMapCanvas.h"
diff --git a/GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.cpp b/GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.cpp
index 30155558d628d476fb9da52a27bd88a71c5ee87b..acbcdc35493e831b58f22ce1cd6a41ca8525cdcb 100644
--- a/GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.cpp
+++ b/GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.cpp
@@ -15,8 +15,8 @@
 #include "GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.h"
 #include "Device/Data/DataUtils.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include <QAction>
 #include <QApplication>
 #include <QWidget>
diff --git a/GUI/Views/IntensityDataWidgets/IntensityDataWidget.cpp b/GUI/Views/IntensityDataWidgets/IntensityDataWidget.cpp
index 2b62d873b902b5a82cb26fd43629b3801192a8d8..cb8e28415316710ea7ce16c628b517dcf5385586 100644
--- a/GUI/Views/IntensityDataWidgets/IntensityDataWidget.cpp
+++ b/GUI/Views/IntensityDataWidgets/IntensityDataWidget.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/IntensityDataWidgets/IntensityDataWidget.h"
-#include "GUI/Session/DataItemUtils.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/DataItemUtils.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataCanvas.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataFFTPresenter.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataPropertyWidget.h"
diff --git a/GUI/Views/IntensityDataWidgets/Plot1D.cpp b/GUI/Views/IntensityDataWidgets/Plot1D.cpp
index 43739db9fb08ff9afb4e6085c4400db7c031b5ef..32e21f82176b7c16762ac09b968624602759385e 100644
--- a/GUI/Views/IntensityDataWidgets/Plot1D.cpp
+++ b/GUI/Views/IntensityDataWidgets/Plot1D.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/IntensityDataWidgets/Plot1D.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/Data1DViewItem.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/Data1DViewItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
 #include "GUI/CommonWidgets/UpdateTimer.h"
diff --git a/GUI/Views/IntensityDataWidgets/PropertyRepeater.cpp b/GUI/Views/IntensityDataWidgets/PropertyRepeater.cpp
index 86131b41d3e65eebcab81e503518bc2582887bcc..3cf7d1d4fca050f2be1ba271d24c3378e08a8aaa 100644
--- a/GUI/Views/IntensityDataWidgets/PropertyRepeater.cpp
+++ b/GUI/Views/IntensityDataWidgets/PropertyRepeater.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/IntensityDataWidgets/PropertyRepeater.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
 
 PropertyRepeater::PropertyRepeater(QObject* parent, bool repeat_child_properties)
     : QObject(parent), m_block_repeater(false), m_repeat_child_properties(repeat_child_properties)
diff --git a/GUI/Views/JobWidgets/FitComparisonController.cpp b/GUI/Views/JobWidgets/FitComparisonController.cpp
index f9dfe61954c4d5304bd3a33833c5c004cd4c1ad0..bd637cc3562d0da8c6c055979ac9fc6c12faaca8 100644
--- a/GUI/Views/JobWidgets/FitComparisonController.cpp
+++ b/GUI/Views/JobWidgets/FitComparisonController.cpp
@@ -14,12 +14,12 @@
 
 #include "GUI/Views/JobWidgets/FitComparisonController.h"
 #include "Device/Data/DataUtils.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/PropertyRepeater.h"
 
 namespace {
diff --git a/GUI/Views/JobWidgets/FitComparisonViewController.cpp b/GUI/Views/JobWidgets/FitComparisonViewController.cpp
index d5432b4241e4fa9ec0c9996699ee3deb732ad530..613fe1f344c461f725d5482b010d7c7ea501e593 100644
--- a/GUI/Views/JobWidgets/FitComparisonViewController.cpp
+++ b/GUI/Views/JobWidgets/FitComparisonViewController.cpp
@@ -14,15 +14,15 @@
 
 #include "GUI/Views/JobWidgets/FitComparisonViewController.h"
 #include "Device/Data/DataUtils.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/Data1DViewItem.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/Data1DViewItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/PropertyRepeater.h"
 
 namespace {
diff --git a/GUI/Views/JobWidgets/FitComparisonWidget.cpp b/GUI/Views/JobWidgets/FitComparisonWidget.cpp
index f0a376d4718b037542d53218e4dadb1e0bf2f100..71f56393b161dec7ba7167e507e9d0e0762c1933 100644
--- a/GUI/Views/JobWidgets/FitComparisonWidget.cpp
+++ b/GUI/Views/JobWidgets/FitComparisonWidget.cpp
@@ -13,10 +13,10 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/FitComparisonWidget.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMapCanvas.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataPropertyWidget.h"
diff --git a/GUI/Views/JobWidgets/FitComparisonWidget1D.cpp b/GUI/Views/JobWidgets/FitComparisonWidget1D.cpp
index 6451a852ccd01ab280b2981c396fa5304443c679..469f51a290ceca2e12f2a4a0b766b89240240b57 100644
--- a/GUI/Views/JobWidgets/FitComparisonWidget1D.cpp
+++ b/GUI/Views/JobWidgets/FitComparisonWidget1D.cpp
@@ -13,11 +13,11 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/FitComparisonWidget1D.h"
-#include "GUI/Session/Data1DViewItem.h"
-#include "GUI/Session/FitSuiteItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/Data1DViewItem.h"
+#include "GUI/Items/FitSuiteItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataPropertyWidget.h"
 #include "GUI/Views/IntensityDataWidgets/Plot1D.h"
 #include "GUI/Views/IntensityDataWidgets/PlotStatusLabel.h"
diff --git a/GUI/Views/JobWidgets/FitFlowWidget.cpp b/GUI/Views/JobWidgets/FitFlowWidget.cpp
index 5f12fa144a87e40308e5ac3a12e09aa8c0f5eb59..c71449437a697998063187d129b7f55aa59e3f4e 100644
--- a/GUI/Views/JobWidgets/FitFlowWidget.cpp
+++ b/GUI/Views/JobWidgets/FitFlowWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/FitFlowWidget.h"
-#include "GUI/Session/FitSuiteItem.h"
+#include "GUI/Items/FitSuiteItem.h"
 #include "GUI/Views/JobWidgets/HistogramPlot.h"
 #include <QVBoxLayout>
 
diff --git a/GUI/Views/JobWidgets/JobListModel.cpp b/GUI/Views/JobWidgets/JobListModel.cpp
index b080dacb06cfbb3c8a09eaef0a41d7d211e4da0b..5ea700e9123f50fff2279a2e52d3608b20edd73b 100644
--- a/GUI/Views/JobWidgets/JobListModel.cpp
+++ b/GUI/Views/JobWidgets/JobListModel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobListModel.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 
 //==================================================================================================
diff --git a/GUI/Views/JobWidgets/JobListView.cpp b/GUI/Views/JobWidgets/JobListView.cpp
index 6c97ce8a14467034b657f17c69c76050e1aee28f..b064bdfbb33ce62577d3997e5deea1281db25cb5 100644
--- a/GUI/Views/JobWidgets/JobListView.cpp
+++ b/GUI/Views/JobWidgets/JobListView.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobListView.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/CommonWidgets/StyledToolBar.h"
 #include "GUI/Views/JobWidgets/JobListModel.h"
diff --git a/GUI/Views/JobWidgets/JobListViewDelegate.cpp b/GUI/Views/JobWidgets/JobListViewDelegate.cpp
index 3ccf587b768b8b3c3e07ac7fa9e818ab379ca13d..eb14a8d46a6f681921200b2134cb59d14215bd7a 100644
--- a/GUI/Views/JobWidgets/JobListViewDelegate.cpp
+++ b/GUI/Views/JobWidgets/JobListViewDelegate.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobListViewDelegate.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/JobWidgets/JobListModel.h"
 #include <QApplication>
 #include <QMouseEvent>
diff --git a/GUI/Views/JobWidgets/JobPropertiesTableModel.cpp b/GUI/Views/JobWidgets/JobPropertiesTableModel.cpp
index 965de3081232fa74581b25824f5acc5f4ecadecd..900eac745fa2fba858a334469de5e1cd48841cdd 100644
--- a/GUI/Views/JobWidgets/JobPropertiesTableModel.cpp
+++ b/GUI/Views/JobWidgets/JobPropertiesTableModel.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobPropertiesTableModel.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include <QLocale>
 
 namespace {
diff --git a/GUI/Views/JobWidgets/JobPropertiesWidget.cpp b/GUI/Views/JobWidgets/JobPropertiesWidget.cpp
index 4f073bbeeb9df303e6eb242c9acfd9135c173e41..6bc7fc775111b9a6b4197379ee34bf3b7ebaa894 100644
--- a/GUI/Views/JobWidgets/JobPropertiesWidget.cpp
+++ b/GUI/Views/JobWidgets/JobPropertiesWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobPropertiesWidget.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/JobWidgets/JobPropertiesTableModel.h"
 #include "GUI/utils/mainwindow_constants.h"
diff --git a/GUI/Views/JobWidgets/JobResultsPresenter.cpp b/GUI/Views/JobWidgets/JobResultsPresenter.cpp
index 96eed62214f30d8303cdf6e8be888da4fab7758b..1e4443d36791e3978cba48ff060b3f4279c09742 100644
--- a/GUI/Views/JobWidgets/JobResultsPresenter.cpp
+++ b/GUI/Views/JobWidgets/JobResultsPresenter.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobResultsPresenter.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataWidget.h"
 #include "GUI/Views/JobWidgets/FitComparisonWidget.h"
 #include "GUI/Views/JobWidgets/FitComparisonWidget1D.h"
diff --git a/GUI/Views/JobWidgets/JobSelectorWidget.cpp b/GUI/Views/JobWidgets/JobSelectorWidget.cpp
index d9bc1d8d11e973a654c7491242a7ccd4dbbd94a9..d09819d36b8d5ce221ae7a6446be5f2a899ca1b4 100644
--- a/GUI/Views/JobWidgets/JobSelectorWidget.cpp
+++ b/GUI/Views/JobWidgets/JobSelectorWidget.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/JobWidgets/JobSelectorWidget.h"
 #include "Base/Utils/Assert.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Views/JobWidgets/JobListView.h"
 #include "GUI/Views/JobWidgets/JobPropertiesWidget.h"
 #include "GUI/utils/mainwindow_constants.h"
diff --git a/GUI/Views/JobWidgets/JobView.cpp b/GUI/Views/JobWidgets/JobView.cpp
index a22953c4674d2a8780a47250a4539f163489a704..710997fdca7c95e06a0a3b301ca528e2c32e1bb5 100644
--- a/GUI/Views/JobWidgets/JobView.cpp
+++ b/GUI/Views/JobWidgets/JobView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/JobWidgets/JobView.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/CommonWidgets/DocksController.h"
 #include "GUI/Views/FitWidgets/FitActivityPanel.h"
diff --git a/GUI/Views/MaskWidgets/EllipseView.cpp b/GUI/Views/MaskWidgets/EllipseView.cpp
index a70403976c44bbc195ae671d7469d63c670bf05d..b420c6ccf46984cdcd5e6f5b3cf3fe44c1adef3b 100644
--- a/GUI/Views/MaskWidgets/EllipseView.cpp
+++ b/GUI/Views/MaskWidgets/EllipseView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/EllipseView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 
diff --git a/GUI/Views/MaskWidgets/IShape2DView.cpp b/GUI/Views/MaskWidgets/IShape2DView.cpp
index b5249dfd9927d5c7e553a03349a712db8130337d..dbd65922896f4fade93d23faacc203082ee779b9 100644
--- a/GUI/Views/MaskWidgets/IShape2DView.cpp
+++ b/GUI/Views/MaskWidgets/IShape2DView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/IShape2DView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/MaskWidgets/ISceneAdaptor.h"
 #include <QAction>
 #include <QGraphicsScene>
diff --git a/GUI/Views/MaskWidgets/LineViews.cpp b/GUI/Views/MaskWidgets/LineViews.cpp
index a5891bee9880c57849bc3cbe30efa593ab08cd48..378aabc02300b042507a6a8f46316502c71efb42 100644
--- a/GUI/Views/MaskWidgets/LineViews.cpp
+++ b/GUI/Views/MaskWidgets/LineViews.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/LineViews.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/MaskWidgets/ColorMapSceneAdaptor.h"
 #include <QCursor>
 #include <QPainter>
diff --git a/GUI/Views/MaskWidgets/MaskAllView.cpp b/GUI/Views/MaskWidgets/MaskAllView.cpp
index 98bd6f09eb05343af5e8341a667b1fcf3a8fca34..854dcfce79c8ffe7b0f069dc2b4820c915fe0dd4 100644
--- a/GUI/Views/MaskWidgets/MaskAllView.cpp
+++ b/GUI/Views/MaskWidgets/MaskAllView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskAllView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/MaskWidgets/ColorMapSceneAdaptor.h"
 #include <QBrush>
 #include <QPainter>
diff --git a/GUI/Views/MaskWidgets/MaskContainerView.cpp b/GUI/Views/MaskWidgets/MaskContainerView.cpp
index 41897835d60aba635ac92e6ec17aa0e37e6bc80e..623a17cb5c8f100dac704de750003de052b8b55d 100644
--- a/GUI/Views/MaskWidgets/MaskContainerView.cpp
+++ b/GUI/Views/MaskWidgets/MaskContainerView.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskContainerView.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Views/MaskWidgets/ISceneAdaptor.h"
 #include <QBrush>
 #include <QPainter>
diff --git a/GUI/Views/MaskWidgets/MaskDrawingContext.cpp b/GUI/Views/MaskWidgets/MaskDrawingContext.cpp
index 93deeda8ec715bb48ac54bc0c419d415cf517050..2f352d65172d2a9ab8a6a3b00c62a8b80cb195c6 100644
--- a/GUI/Views/MaskWidgets/MaskDrawingContext.cpp
+++ b/GUI/Views/MaskWidgets/MaskDrawingContext.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskDrawingContext.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 
 MaskDrawingContext::MaskDrawingContext()
     : m_current_activity(MaskEditorFlags::PAN_ZOOM_MODE)
diff --git a/GUI/Views/MaskWidgets/MaskEditor.cpp b/GUI/Views/MaskWidgets/MaskEditor.cpp
index 92f0ae5dee96fc82de20687d2933acb8016011ce..7a7463918c1fd773db5be3a2b280ee54128c27cf 100644
--- a/GUI/Views/MaskWidgets/MaskEditor.cpp
+++ b/GUI/Views/MaskWidgets/MaskEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskEditor.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/MaskWidgets/MaskEditorActions.h"
 #include "GUI/Views/MaskWidgets/MaskEditorCanvas.h"
 #include "GUI/Views/MaskWidgets/MaskEditorPropertyPanel.h"
diff --git a/GUI/Views/MaskWidgets/MaskEditorActions.cpp b/GUI/Views/MaskWidgets/MaskEditorActions.cpp
index eb3168e64f11d76ecac406274dbf3db5afc27a6d..26ced3c2ae5c23bb3332de0f48f86eee14e2f8ce 100644
--- a/GUI/Views/MaskWidgets/MaskEditorActions.cpp
+++ b/GUI/Views/MaskWidgets/MaskEditorActions.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskEditorActions.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/SessionModel.h"
 #include <QAction>
 #include <QItemSelectionModel>
 #include <QMenu>
diff --git a/GUI/Views/MaskWidgets/MaskEditorCanvas.cpp b/GUI/Views/MaskWidgets/MaskEditorCanvas.cpp
index 35c5c067a8d4a1dbd4dba35b1aa57d010c8ee9b6..02e7e3554c4637fecb1f4c97a09c86450b7b74d8 100644
--- a/GUI/Views/MaskWidgets/MaskEditorCanvas.cpp
+++ b/GUI/Views/MaskWidgets/MaskEditorCanvas.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskEditorCanvas.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/IntensityDataWidgets/PlotStatusLabel.h"
 #include "GUI/Views/IntensityDataWidgets/SavePlotAssistant.h"
diff --git a/GUI/Views/MaskWidgets/MaskEditorPropertyPanel.cpp b/GUI/Views/MaskWidgets/MaskEditorPropertyPanel.cpp
index ed680551218decac23c52ed8348baf4f1ac72885..8d426dc162a1b26f965e08c6e4e23c75c181757a 100644
--- a/GUI/Views/MaskWidgets/MaskEditorPropertyPanel.cpp
+++ b/GUI/Views/MaskWidgets/MaskEditorPropertyPanel.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskEditorPropertyPanel.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/PropertyEditor/ComponentEditor.h"
 
 #include <qAccordion/contentpane.h>
diff --git a/GUI/Views/MaskWidgets/MaskGraphicsProxy.cpp b/GUI/Views/MaskWidgets/MaskGraphicsProxy.cpp
index 2059e6379932fa92586a1bf5ca7cb1de1c87529e..dbc570446936827d2f543a3165990e308adccb2f 100644
--- a/GUI/Views/MaskWidgets/MaskGraphicsProxy.cpp
+++ b/GUI/Views/MaskWidgets/MaskGraphicsProxy.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/MaskGraphicsProxy.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/MaskWidgets/ColorMapSceneAdaptor.h"
 #include <QGraphicsSceneMouseEvent>
diff --git a/GUI/Views/MaskWidgets/MaskGraphicsScene.cpp b/GUI/Views/MaskWidgets/MaskGraphicsScene.cpp
index 0dc4284013a1ccaf4c03161898bafa73edb97503..4ab7efdb9e3c955d5ee0f8dc35c54db968e0cba6 100644
--- a/GUI/Views/MaskWidgets/MaskGraphicsScene.cpp
+++ b/GUI/Views/MaskWidgets/MaskGraphicsScene.cpp
@@ -14,11 +14,11 @@
 
 #include "GUI/Views/MaskWidgets/MaskGraphicsScene.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/MaskWidgets/ColorMapSceneAdaptor.h"
 #include "GUI/Views/MaskWidgets/MaskGraphicsProxy.h"
 #include "GUI/Views/MaskWidgets/MaskViewFactory.h"
diff --git a/GUI/Views/MaskWidgets/MaskResultsPresenter.cpp b/GUI/Views/MaskWidgets/MaskResultsPresenter.cpp
index 422b7a4e910a1d61a226eac3b85a84a5c3aa3430..63e58309e3446b8090380254413c8de6ce37d04f 100644
--- a/GUI/Views/MaskWidgets/MaskResultsPresenter.cpp
+++ b/GUI/Views/MaskWidgets/MaskResultsPresenter.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Views/MaskWidgets/MaskResultsPresenter.h"
 #include "Device/Mask/DetectorMask.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/SessionModel.h"
 #include <QVBoxLayout>
 
 MaskResultsPresenter::MaskResultsPresenter(QWidget* parent)
diff --git a/GUI/Views/MaskWidgets/MaskViewFactory.cpp b/GUI/Views/MaskWidgets/MaskViewFactory.cpp
index e69d7980c0ee580cfeba2fd6680619578f4ae436..bb79755a9eb5230a5357f38a7eaec3eb3002ebe8 100644
--- a/GUI/Views/MaskWidgets/MaskViewFactory.cpp
+++ b/GUI/Views/MaskWidgets/MaskViewFactory.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Views/MaskWidgets/MaskViewFactory.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/Views/MaskWidgets/EllipseView.h"
 #include "GUI/Views/MaskWidgets/LineViews.h"
 #include "GUI/Views/MaskWidgets/MaskAllView.h"
diff --git a/GUI/Views/MaskWidgets/PolygonPointView.cpp b/GUI/Views/MaskWidgets/PolygonPointView.cpp
index 1e0ef947e623f0bbe467e02047a1e1ab418c99be..312d6c72acbf66628d3cc4ce567919d8d7e98750 100644
--- a/GUI/Views/MaskWidgets/PolygonPointView.cpp
+++ b/GUI/Views/MaskWidgets/PolygonPointView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/PolygonPointView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 
diff --git a/GUI/Views/MaskWidgets/PolygonView.cpp b/GUI/Views/MaskWidgets/PolygonView.cpp
index 8bce81f32f8e8b59a588db6e318a1c6d9b79f9bf..6992be507071af40d59dbb1cfa558aa82cddaaf2 100644
--- a/GUI/Views/MaskWidgets/PolygonView.cpp
+++ b/GUI/Views/MaskWidgets/PolygonView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/PolygonView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/MaskWidgets/PolygonPointView.h"
 #include <QCursor>
 #include <QPainter>
diff --git a/GUI/Views/MaskWidgets/RectangleView.cpp b/GUI/Views/MaskWidgets/RectangleView.cpp
index cdf8cb09ec2d1d8e37ae3ec1dfe457b3cb179021..905033b0e158f980272ef3f4376d0a0de7f951f0 100644
--- a/GUI/Views/MaskWidgets/RectangleView.cpp
+++ b/GUI/Views/MaskWidgets/RectangleView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/RectangleView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 
diff --git a/GUI/Views/MaskWidgets/RegionOfInterestView.cpp b/GUI/Views/MaskWidgets/RegionOfInterestView.cpp
index e7417403768902aa24baec270a5fdd43871b57b8..7d0b44caa46a54f62721e0960eb61479b1930d72 100644
--- a/GUI/Views/MaskWidgets/RegionOfInterestView.cpp
+++ b/GUI/Views/MaskWidgets/RegionOfInterestView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaskWidgets/RegionOfInterestView.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/MaskWidgets/ISceneAdaptor.h"
 #include <QPainter>
 
diff --git a/GUI/Views/MaterialEditor/MaterialEditorDialog.cpp b/GUI/Views/MaterialEditor/MaterialEditorDialog.cpp
index 8642870a9e5665eb7f655d3dad41d122a468f356..704c6c3655c11eb427ca15a19a233f2c301c1757 100644
--- a/GUI/Views/MaterialEditor/MaterialEditorDialog.cpp
+++ b/GUI/Views/MaterialEditor/MaterialEditorDialog.cpp
@@ -14,12 +14,12 @@
 
 #include "GUI/Views/MaterialEditor/MaterialEditorDialog.h"
 #include "GUI/Application/Application.h"
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Material/MaterialModelStore.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/CommonWidgets/GUIHelpers.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/MaterialEditor/MaterialEditorModel.h"
diff --git a/GUI/Views/MaterialEditor/MaterialEditorModel.cpp b/GUI/Views/MaterialEditor/MaterialEditorModel.cpp
index b6c1a1a683d908c323b8ef4fe2912b40d24581b4..9699b4085d06be30243f048a56bed104e9659cdc 100644
--- a/GUI/Views/MaterialEditor/MaterialEditorModel.cpp
+++ b/GUI/Views/MaterialEditor/MaterialEditorModel.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/MaterialEditor/MaterialEditorModel.h"
-#include "GUI/Session/MaterialItem.h"
+#include "GUI/Items/MaterialItem.h"
 #include "GUI/Models/Material/MaterialModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include <QApplication>
 #include <QFontMetrics>
 #include <QPixmap>
diff --git a/GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.cpp b/GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.cpp
index 36f3804b18becf39d5708762cfe0912b3ce3f8f2..bb3fd29dbe3f52a62825c5902899c627b1e3c2a7 100644
--- a/GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.cpp
+++ b/GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ProjectionsWidgets/IntensityDataProjectionsWidget.h"
-#include "GUI/Session/DataItemUtils.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/DataItemUtils.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditor.h"
 #include <QVBoxLayout>
 
diff --git a/GUI/Views/ProjectionsWidgets/ProjectionsEditor.cpp b/GUI/Views/ProjectionsWidgets/ProjectionsEditor.cpp
index 0ba5980ef43aa5ec2ec7f27569a5a2f95f3475c5..1a7b90d596e82729c921ec5c9f25146ccad9b9e9 100644
--- a/GUI/Views/ProjectionsWidgets/ProjectionsEditor.cpp
+++ b/GUI/Views/ProjectionsWidgets/ProjectionsEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditor.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.h"
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.h"
 #include "GUI/Views/ProjectionsWidgets/ProjectionsPropertyPanel.h"
diff --git a/GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.cpp b/GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.cpp
index b02bf1a4e7479398d8017e5c833c8e80bf9e0a25..9da347f569daa65955743b6dc8887ae0770312f5 100644
--- a/GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.cpp
+++ b/GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditorActions.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/ProjectionsWidgets/SaveProjectionsAssistant.h"
 #include <QAction>
 #include <QItemSelectionModel>
diff --git a/GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.cpp b/GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.cpp
index 56c91191758fda7da79fd90f3f334ad1ffca90bf..be6f618cc8ebf1eb25e8ee7dfac3e92a29c8f4d7 100644
--- a/GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.cpp
+++ b/GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ProjectionsWidgets/ProjectionsEditorCanvas.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMap.h"
 #include "GUI/Views/IntensityDataWidgets/PlotStatusLabel.h"
 #include "GUI/Views/IntensityDataWidgets/ScientificPlotEvent.h"
diff --git a/GUI/Views/ProjectionsWidgets/ProjectionsPlot.cpp b/GUI/Views/ProjectionsWidgets/ProjectionsPlot.cpp
index 72a23b31b8d062aff95b0b4709ee3d9dc0f313c8..ea3e47acf64b710c482265d6202cebc248dd3c6d 100644
--- a/GUI/Views/ProjectionsWidgets/ProjectionsPlot.cpp
+++ b/GUI/Views/ProjectionsWidgets/ProjectionsPlot.cpp
@@ -15,10 +15,10 @@
 #include "GUI/Views/ProjectionsWidgets/ProjectionsPlot.h"
 #include "Device/Histo/Histogram1D.h"
 #include "Device/Histo/Histogram2D.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMapUtils.h"
 #include "GUI/Views/IntensityDataWidgets/plot_constants.h"
 #include <qcustomplot.h>
diff --git a/GUI/Views/ProjectionsWidgets/ProjectionsWidget.cpp b/GUI/Views/ProjectionsWidgets/ProjectionsWidget.cpp
index 184f52f9779c56f679040985e0621f67ea83cea7..f64b85980df01099737175246cd4c8c8c95caf03 100644
--- a/GUI/Views/ProjectionsWidgets/ProjectionsWidget.cpp
+++ b/GUI/Views/ProjectionsWidgets/ProjectionsWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/ProjectionsWidgets/ProjectionsWidget.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Views/ProjectionsWidgets/ProjectionsPlot.h"
 #include <QTabWidget>
 #include <QVBoxLayout>
diff --git a/GUI/Views/ProjectionsWidgets/SaveProjectionsAssistant.cpp b/GUI/Views/ProjectionsWidgets/SaveProjectionsAssistant.cpp
index 8cfd7c861655951c43ab464a26be29bc3e90385a..bf2be141996198e48407bc85a8de54293130170f 100644
--- a/GUI/Views/ProjectionsWidgets/SaveProjectionsAssistant.cpp
+++ b/GUI/Views/ProjectionsWidgets/SaveProjectionsAssistant.cpp
@@ -18,9 +18,9 @@
 #include "Device/Histo/Histogram2D.h"
 #include "GUI/Application/Application.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Project/ProjectUtils.h"
 #include "GUI/Project/projectmanager.h"
 #include <QFileDialog>
diff --git a/GUI/Views/PropertyEditor/ComponentFlatView.cpp b/GUI/Views/PropertyEditor/ComponentFlatView.cpp
index 8d20393b9e16c39cabce57913d20e68a89bf33fd..e76cd35117bee8d1da9861cd0e5c043a8c3855de 100644
--- a/GUI/Views/PropertyEditor/ComponentFlatView.cpp
+++ b/GUI/Views/PropertyEditor/ComponentFlatView.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Views/PropertyEditor/ComponentFlatView.h"
 #include "GUI/Mapper/ComponentUtils.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/PropertyEditor/PropertyEditorFactory.h"
 #include "GUI/Views/PropertyEditor/PropertyWidgetItem.h"
 #include "GUI/utils/LayoutUtils.h"
diff --git a/GUI/Views/PropertyEditor/ComponentTreeActions.cpp b/GUI/Views/PropertyEditor/ComponentTreeActions.cpp
index 4aeac6e815e7b87eff7fd3950a84bef8da3a036e..f52533336232a51638cc09a6b0fb5e9923a2d00a 100644
--- a/GUI/Views/PropertyEditor/ComponentTreeActions.cpp
+++ b/GUI/Views/PropertyEditor/ComponentTreeActions.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/PropertyEditor/ComponentTreeActions.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include <QAction>
 #include <QMenu>
 
diff --git a/GUI/Views/PropertyEditor/ComponentTreeView.cpp b/GUI/Views/PropertyEditor/ComponentTreeView.cpp
index 24e2c456269fd0cab361f9ba52974e47a9aa3d01..984fbb4e7cbb1ae8e243ed07670a6bc8a854293c 100644
--- a/GUI/Views/PropertyEditor/ComponentTreeView.cpp
+++ b/GUI/Views/PropertyEditor/ComponentTreeView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/PropertyEditor/ComponentTreeView.h"
 #include "GUI/Mapper/ComponentProxyModel.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/PropertyEditor/ComponentTreeActions.h"
 #include "GUI/Views/PropertyEditor/SessionModelDelegate.h"
diff --git a/GUI/Views/PropertyEditor/CustomEditors.cpp b/GUI/Views/PropertyEditor/CustomEditors.cpp
index 4f34cede31c232f8ac7aa089affc951a7195bb0e..cb063ca6560fad03531dba2d814f9db778ca20d3 100644
--- a/GUI/Views/PropertyEditor/CustomEditors.cpp
+++ b/GUI/Views/PropertyEditor/CustomEditors.cpp
@@ -16,7 +16,7 @@
 #include "Base/Utils/Assert.h"
 #include "Fit/Param/RealLimits.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/CommonWidgets/ScientificSpinBox.h"
 #include "GUI/Views/MaterialEditor/MaterialEditorDialog.h"
 #include "GUI/Project/projectmanager.h"
diff --git a/GUI/Views/PropertyEditor/PropertyEditorFactory.cpp b/GUI/Views/PropertyEditor/PropertyEditorFactory.cpp
index 2f5d78c2417e7df8a6f9fffe2961c213c3ee9c0a..a2935c4ac5bc44bcd3136d4eec4e9b9764ff275e 100644
--- a/GUI/Views/PropertyEditor/PropertyEditorFactory.cpp
+++ b/GUI/Views/PropertyEditor/PropertyEditorFactory.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Views/PropertyEditor/PropertyEditorFactory.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/MaterialItemUtils.h"
-#include "GUI/Session/SessionFlags.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/MaterialItemUtils.h"
+#include "GUI/Items/SessionFlags.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/CommonWidgets/ScientificSpinBox.h"
 #include "GUI/Views/PropertyEditor/MultiComboPropertyEditor.h"
 #include <QLabel>
diff --git a/GUI/Views/PropertyEditor/PropertyWidgetItem.cpp b/GUI/Views/PropertyEditor/PropertyWidgetItem.cpp
index 50141e0da9112f0876e6a875703488789b7742dd..108345f95066bac623b7732b907c8e274a90ae51 100644
--- a/GUI/Views/PropertyEditor/PropertyWidgetItem.cpp
+++ b/GUI/Views/PropertyEditor/PropertyWidgetItem.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/PropertyEditor/PropertyWidgetItem.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/PropertyEditor/CustomEditors.h"
 #include "GUI/Views/PropertyEditor/SessionModelDelegate.h"
 #include <QComboBox>
diff --git a/GUI/Views/PropertyEditor/SessionModelDelegate.cpp b/GUI/Views/PropertyEditor/SessionModelDelegate.cpp
index 104c9c889875a83627459631c04b1c807cecfbdb..2bcb78ad8dccec7ac97ce045b25a8c60f40b7008 100644
--- a/GUI/Views/PropertyEditor/SessionModelDelegate.cpp
+++ b/GUI/Views/PropertyEditor/SessionModelDelegate.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/PropertyEditor/SessionModelDelegate.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/Views/PropertyEditor/CustomEditors.h"
 #include "GUI/Views/PropertyEditor/PropertyEditorFactory.h"
 #include "GUI/utils/CustomEventFilters.h"
diff --git a/GUI/Views/PropertyEditor/TestComponentView.cpp b/GUI/Views/PropertyEditor/TestComponentView.cpp
index 5eab58a288a06fc975829184f0081f63e97e2342..05dd5aa37ba888dd5f577a56bbc2da4251aafda6 100644
--- a/GUI/Views/PropertyEditor/TestComponentView.cpp
+++ b/GUI/Views/PropertyEditor/TestComponentView.cpp
@@ -13,14 +13,14 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/PropertyEditor/TestComponentView.h"
-#include "GUI/Session/BeamItems.h"
+#include "GUI/Items/BeamItems.h"
 #include "GUI/Models/Sample/GUIDomainSampleVisitor.h"
 #include "GUI/Models/Data/GUIObjectBuilder.h"
-#include "GUI/Session/IntensityDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
 #include "GUI/Models/Material/MaterialModel.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/PropertyEditor/ComponentEditor.h"
 #include "GUI/Views/PropertyEditor/SessionModelDelegate.h"
diff --git a/GUI/Views/RealSpaceWidgets/RealSpaceBuilder.cpp b/GUI/Views/RealSpaceWidgets/RealSpaceBuilder.cpp
index 1c3029f8884f44b738b35e90a54aa4479d9d9470..d268d3ffebf90ebab82ca183dbffa9665b9ffe21 100644
--- a/GUI/Views/RealSpaceWidgets/RealSpaceBuilder.cpp
+++ b/GUI/Views/RealSpaceWidgets/RealSpaceBuilder.cpp
@@ -14,14 +14,14 @@
 
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilder.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Views/RealSpaceWidgets/Particle3DContainer.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceCanvas.h"
diff --git a/GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.cpp b/GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.cpp
index b54b23b4387329336945f4e36429780a27ad197c..14112e616c8865492df41ceca1a19146e9301c72 100644
--- a/GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.cpp
+++ b/GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.cpp
@@ -15,14 +15,14 @@
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.h"
 #include "Base/Const/Units.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/MaterialItem.h"
+#include "GUI/Items/MaterialItem.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Material/MaterialModelStore.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Views/RealSpaceWidgets/Particle3DContainer.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilder.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceCanvas.h"
diff --git a/GUI/Views/RealSpaceWidgets/RealSpaceCanvas.cpp b/GUI/Views/RealSpaceWidgets/RealSpaceCanvas.cpp
index 794635642aa154f0e1ce2a500edf5876f343c686..1fc7aae040ced9d90cef8d3e016a9532a58dbab2 100644
--- a/GUI/Views/RealSpaceWidgets/RealSpaceCanvas.cpp
+++ b/GUI/Views/RealSpaceWidgets/RealSpaceCanvas.cpp
@@ -16,7 +16,7 @@
 #include "GUI/Application/Application.h"
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "GUI/InfoWidgets/CautionSign.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilder.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceModel.h"
diff --git a/GUI/Views/RealSpaceWidgets/RealSpaceMesoCrystalUtils.cpp b/GUI/Views/RealSpaceWidgets/RealSpaceMesoCrystalUtils.cpp
index 5dc1fbf8be18848fdeee4c25bf1edc4f66986acb..2c671c0c59978441ee7722299ddc2e96da36cbcc 100644
--- a/GUI/Views/RealSpaceWidgets/RealSpaceMesoCrystalUtils.cpp
+++ b/GUI/Views/RealSpaceWidgets/RealSpaceMesoCrystalUtils.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Views/RealSpaceWidgets/RealSpaceMesoCrystalUtils.h"
 #include "Base/Const/Units.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
 #include "GUI/Views/RealSpaceWidgets/Particle3DContainer.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilderUtils.h"
 #include "GUI/Views/RealSpaceWidgets/TransformTo3D.h"
diff --git a/GUI/Views/RealSpaceWidgets/TransformTo3D.cpp b/GUI/Views/RealSpaceWidgets/TransformTo3D.cpp
index c92c1c43a0644f6ea88130d7484130e8a89806f6..f790ad6d5ec38f58ef215a661d87ba3447bcce30 100644
--- a/GUI/Views/RealSpaceWidgets/TransformTo3D.cpp
+++ b/GUI/Views/RealSpaceWidgets/TransformTo3D.cpp
@@ -14,10 +14,10 @@
 
 #include "GUI/Views/RealSpaceWidgets/TransformTo3D.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceCanvas.h"
 #include "Sample/HardParticle/HardParticles.h"
 
diff --git a/GUI/Views/SampleDesigner/ConnectableView.cpp b/GUI/Views/SampleDesigner/ConnectableView.cpp
index 0aecea42c74febe6d177ee79c89ff230f8780b00..961cd4a99b33b2e0e126e87083f958b2c3d8185a 100644
--- a/GUI/Views/SampleDesigner/ConnectableView.cpp
+++ b/GUI/Views/SampleDesigner/ConnectableView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/SampleDesigner/ConnectableView.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/SampleDesigner/NodeEditorConnection.h"
diff --git a/GUI/Views/SampleDesigner/DesignerScene.cpp b/GUI/Views/SampleDesigner/DesignerScene.cpp
index e9aca1565b36af59f6f8a3bad4beb9d53144fe24..6d3cf868fd9f37e8d07571565139c3f264c9e978 100644
--- a/GUI/Views/SampleDesigner/DesignerScene.cpp
+++ b/GUI/Views/SampleDesigner/DesignerScene.cpp
@@ -15,14 +15,14 @@
 #include "GUI/Views/SampleDesigner/DesignerScene.h"
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
 #include "GUI/Models/Sample/GUIExamplesFactory.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/ItemFactory.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/RotationItems.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/ItemFactory.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/RotationItems.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/Views/SampleDesigner/DesignerMimeData.h"
diff --git a/GUI/Views/SampleDesigner/ILayerView.cpp b/GUI/Views/SampleDesigner/ILayerView.cpp
index 70d93e1d4102518c8830679bc6b92fa61053b174..a8ee9a04b4713767732f95b8ba844981bbdcf1a5 100644
--- a/GUI/Views/SampleDesigner/ILayerView.cpp
+++ b/GUI/Views/SampleDesigner/ILayerView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Models/Types/DoubleDescriptor.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/LayerItem.h"
+#include "GUI/Items/LayerItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/Views/SampleDesigner/DesignerScene.h"
diff --git a/GUI/Views/SampleDesigner/IView.cpp b/GUI/Views/SampleDesigner/IView.cpp
index 0d327cfa404285a9ad922fe181a66f5b53e229c7..6486337409c434ea7102357e599869a26a1a99c6 100644
--- a/GUI/Views/SampleDesigner/IView.cpp
+++ b/GUI/Views/SampleDesigner/IView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/IView.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 #include <QString>
 
 IView::IView(QGraphicsItem* parent) : QGraphicsObject(parent), m_item(nullptr)
diff --git a/GUI/Views/SampleDesigner/InterferenceForm.cpp b/GUI/Views/SampleDesigner/InterferenceForm.cpp
index f4c29cac04ea602a015eb8a6cebd9a9032f87500..29dadd5bc509a5594ccddd76a26968a187caf115 100644
--- a/GUI/Views/SampleDesigner/InterferenceForm.cpp
+++ b/GUI/Views/SampleDesigner/InterferenceForm.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/InterferenceForm.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/FormLayouter.h"
 #include "GUI/Views/SampleDesigner/SampleEditorController.h"
diff --git a/GUI/Views/SampleDesigner/ItemTreeView.cpp b/GUI/Views/SampleDesigner/ItemTreeView.cpp
index 7fa93cf3333a1b7fed4f754d977a05d9a59fd551..f68f1952391433fd3973566da2f1378356dbba44 100644
--- a/GUI/Views/SampleDesigner/ItemTreeView.cpp
+++ b/GUI/Views/SampleDesigner/ItemTreeView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/ItemTreeView.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include <QDragMoveEvent>
 #include <QMimeData>
 #include <QtCore/QXmlStreamWriter>
diff --git a/GUI/Views/SampleDesigner/LayerEditorUtils.cpp b/GUI/Views/SampleDesigner/LayerEditorUtils.cpp
index f7aa1087b31d6e7d02d8ee07bb20cbdd6cfb0624..5a429ba94943e8040e07d2acab231788b01b7490 100644
--- a/GUI/Views/SampleDesigner/LayerEditorUtils.cpp
+++ b/GUI/Views/SampleDesigner/LayerEditorUtils.cpp
@@ -13,15 +13,15 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/LayerEditorUtils.h"
-#include "GUI/Session/FTDecayFunctionItems.h"
-#include "GUI/Session/FTDistributionItems.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/RotationItems.h"
+#include "GUI/Items/FTDecayFunctionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/RotationItems.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/DoubleSpinBox.h"
 #include "GUI/Views/SampleDesigner/MesoCrystalForm.h"
diff --git a/GUI/Views/SampleDesigner/LayerForm.cpp b/GUI/Views/SampleDesigner/LayerForm.cpp
index 265c774eb0121641cd2efbdb4033e1a4f6f79d74..9dc0ce3ddbe6a24ae9c31cb65ee4f229a5c2eeb4 100644
--- a/GUI/Views/SampleDesigner/LayerForm.cpp
+++ b/GUI/Views/SampleDesigner/LayerForm.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/LayerForm.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Types/UIntDescriptor.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/MaterialInplaceForm.h"
diff --git a/GUI/Views/SampleDesigner/LayerOrientedSampleEditor.cpp b/GUI/Views/SampleDesigner/LayerOrientedSampleEditor.cpp
index ee73c27214762856a06219f13e38b418011ade40..15cc245ff8e430e3c9d7cdce648262caf5f7c990 100644
--- a/GUI/Views/SampleDesigner/LayerOrientedSampleEditor.cpp
+++ b/GUI/Views/SampleDesigner/LayerOrientedSampleEditor.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/LayerOrientedSampleEditor.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/CommonWidgets/StyledToolBar.h"
 #include "GUI/Views/SampleDesigner/LayerEditorUtils.h"
 #include "GUI/Views/SampleDesigner/MultiLayerForm.h"
diff --git a/GUI/Views/SampleDesigner/LayerView.cpp b/GUI/Views/SampleDesigner/LayerView.cpp
index 3d4c309e93b436c76d4ca9ad499042856d4ce122..88c7f1b5c1ec2f876e089975590f71fe615272c0 100644
--- a/GUI/Views/SampleDesigner/LayerView.cpp
+++ b/GUI/Views/SampleDesigner/LayerView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/LayerView.h"
-#include "GUI/Session/LayerItem.h"
+#include "GUI/Items/LayerItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/Views/SampleDesigner/MultiLayerView.h"
 #include "GUI/Views/SampleDesigner/ParticleLayoutView.h"
diff --git a/GUI/Views/SampleDesigner/MaterialInplaceForm.cpp b/GUI/Views/SampleDesigner/MaterialInplaceForm.cpp
index 2c96875a46134ee88669dbff16de44e38ef56e5e..ab0c2bd58a8835f5a7c21e31ce6935fe5728a455 100644
--- a/GUI/Views/SampleDesigner/MaterialInplaceForm.cpp
+++ b/GUI/Views/SampleDesigner/MaterialInplaceForm.cpp
@@ -14,11 +14,11 @@
 
 #include "GUI/Views/SampleDesigner/MaterialInplaceForm.h"
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/ItemWithMaterial.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/ItemWithMaterial.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Material/MaterialModelStore.h"
-#include "GUI/Session/ModelPath.h"
+#include "GUI/Items/ModelPath.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/DoubleLineEdit.h"
 #include "GUI/CommonWidgets/DoubleSpinBox.h"
diff --git a/GUI/Views/SampleDesigner/MesoCrystalForm.cpp b/GUI/Views/SampleDesigner/MesoCrystalForm.cpp
index 65e057d540f9bc1d7403b5e8517de06cf408f42d..458d239f021405d6f25412a8ceebfa8910817ef1 100644
--- a/GUI/Views/SampleDesigner/MesoCrystalForm.cpp
+++ b/GUI/Views/SampleDesigner/MesoCrystalForm.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/MesoCrystalForm.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/FormLayouter.h"
diff --git a/GUI/Views/SampleDesigner/MesoCrystalView.cpp b/GUI/Views/SampleDesigner/MesoCrystalView.cpp
index 21fcdc12aebb5e53c2c9e293fc0a095cc3ceaca8..b5406a7b7bb96e65d0f4a07e442d8028dd089276 100644
--- a/GUI/Views/SampleDesigner/MesoCrystalView.cpp
+++ b/GUI/Views/SampleDesigner/MesoCrystalView.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/MesoCrystalView.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 
diff --git a/GUI/Views/SampleDesigner/MultiLayerForm.cpp b/GUI/Views/SampleDesigner/MultiLayerForm.cpp
index 303bef28836058041cb411097255b5dd0760b9b5..504deedfce3de330579f5457f14766eabb445769 100644
--- a/GUI/Views/SampleDesigner/MultiLayerForm.cpp
+++ b/GUI/Views/SampleDesigner/MultiLayerForm.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/MultiLayerForm.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/DoubleSpinBox.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
diff --git a/GUI/Views/SampleDesigner/MultiLayerView.cpp b/GUI/Views/SampleDesigner/MultiLayerView.cpp
index ca8da18f675feaf4b01e03ef663db61d795f81e8..a04243979f9f357ef4d0f22cda20d3d49af8556a 100644
--- a/GUI/Views/SampleDesigner/MultiLayerView.cpp
+++ b/GUI/Views/SampleDesigner/MultiLayerView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/SampleDesigner/MultiLayerView.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionGraphicsItem.h"
+#include "GUI/Items/SessionGraphicsItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/Views/SampleDesigner/DesignerMimeData.h"
 #include "GUI/Views/SampleDesigner/DesignerScene.h"
diff --git a/GUI/Views/SampleDesigner/ParticleCompositionForm.cpp b/GUI/Views/SampleDesigner/ParticleCompositionForm.cpp
index 9f00deeea5b7f33bcd3d9bd531cedac5308696b7..4dd1fb3ce1fa439fb807c19393b8feb318df26ad 100644
--- a/GUI/Views/SampleDesigner/ParticleCompositionForm.cpp
+++ b/GUI/Views/SampleDesigner/ParticleCompositionForm.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/ParticleCompositionForm.h"
-#include "GUI/Session/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/FormLayouter.h"
diff --git a/GUI/Views/SampleDesigner/ParticleCompositionView.cpp b/GUI/Views/SampleDesigner/ParticleCompositionView.cpp
index c1b86be8ba2bd75a2300e6c33461b844c2c81c2c..11127766c48750e20a838dd12818bfda5517ddc5 100644
--- a/GUI/Views/SampleDesigner/ParticleCompositionView.cpp
+++ b/GUI/Views/SampleDesigner/ParticleCompositionView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/ParticleCompositionView.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 
diff --git a/GUI/Views/SampleDesigner/ParticleCoreShellForm.cpp b/GUI/Views/SampleDesigner/ParticleCoreShellForm.cpp
index 1611e3bfd1b86bfefa3286d496eb742a282188e8..c9004fd32ca4d2f3231b919bddaa17d25a589202 100644
--- a/GUI/Views/SampleDesigner/ParticleCoreShellForm.cpp
+++ b/GUI/Views/SampleDesigner/ParticleCoreShellForm.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Views/SampleDesigner/ParticleCoreShellForm.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/SampleEditorController.h"
diff --git a/GUI/Views/SampleDesigner/ParticleCoreShellView.cpp b/GUI/Views/SampleDesigner/ParticleCoreShellView.cpp
index a2b79c85f0c989332b5341f90c6250ebf18f1179..ff9166f5c69c637921c28dc894528344365e0b67 100644
--- a/GUI/Views/SampleDesigner/ParticleCoreShellView.cpp
+++ b/GUI/Views/SampleDesigner/ParticleCoreShellView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/ParticleCoreShellView.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 
diff --git a/GUI/Views/SampleDesigner/ParticleForm.cpp b/GUI/Views/SampleDesigner/ParticleForm.cpp
index 3c3184e103a6c8ea573ecbce4a637c3381faf056..b994a4a733fd92b99ba2641f0220c36ecc5737ef 100644
--- a/GUI/Views/SampleDesigner/ParticleForm.cpp
+++ b/GUI/Views/SampleDesigner/ParticleForm.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/Views/SampleDesigner/ParticleForm.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Types/VectorDescriptor.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/FormLayouter.h"
diff --git a/GUI/Views/SampleDesigner/ParticleLayoutForm.cpp b/GUI/Views/SampleDesigner/ParticleLayoutForm.cpp
index d2672fea7e769bb6284eb8dfc41f6f3ed6265d7b..470e2289c0193e14d356305312ba18316de57e7d 100644
--- a/GUI/Views/SampleDesigner/ParticleLayoutForm.cpp
+++ b/GUI/Views/SampleDesigner/ParticleLayoutForm.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/ParticleLayoutForm.h"
-#include "GUI/Session/ItemWithParticles.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/ItemWithParticles.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SampleDesigner/InterferenceForm.h"
 #include "GUI/Views/SampleDesigner/LayerEditorUtils.h"
diff --git a/GUI/Views/SampleDesigner/ParticleLayoutView.cpp b/GUI/Views/SampleDesigner/ParticleLayoutView.cpp
index 2f83d388f87059455ed1cf2242850a7a9a149a08..31ac623f4d9e1de1ced2d4e78241dbf66b423c97 100644
--- a/GUI/Views/SampleDesigner/ParticleLayoutView.cpp
+++ b/GUI/Views/SampleDesigner/ParticleLayoutView.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/SampleDesigner/ParticleLayoutView.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/Views/SampleDesigner/ParticleView.h"
 
diff --git a/GUI/Views/SampleDesigner/ParticleView.cpp b/GUI/Views/SampleDesigner/ParticleView.cpp
index bd14e72c0fe361be0ba13e8d77fc49736a8dbcba..9c717c2a0b821cc800843c4b8870ea4fa2acff4c 100644
--- a/GUI/Views/SampleDesigner/ParticleView.cpp
+++ b/GUI/Views/SampleDesigner/ParticleView.cpp
@@ -14,9 +14,9 @@
 
 #include "GUI/Views/SampleDesigner/ParticleView.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include <QObject>
diff --git a/GUI/Views/SampleDesigner/SampleEditorCommands.cpp b/GUI/Views/SampleDesigner/SampleEditorCommands.cpp
index c45493f7c9af32c3fdd898ee20fe217856cbcc20..17c867608799afdd3b0b643506013d84659f4b62 100644
--- a/GUI/Views/SampleDesigner/SampleEditorCommands.cpp
+++ b/GUI/Views/SampleDesigner/SampleEditorCommands.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/SampleEditorCommands.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Views/SampleDesigner/MultiLayerForm.h"
 #include "GUI/Views/SampleDesigner/SampleEditorController.h"
 
diff --git a/GUI/Views/SampleDesigner/SampleEditorController.cpp b/GUI/Views/SampleDesigner/SampleEditorController.cpp
index 000e803ca4ba31b76b08f0f12e793ee579799354..926275cb001c863b0b06ac0e25a34956edcb8368 100644
--- a/GUI/Views/SampleDesigner/SampleEditorController.cpp
+++ b/GUI/Views/SampleDesigner/SampleEditorController.cpp
@@ -13,13 +13,13 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/SampleEditorController.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Types/UIntDescriptor.h"
 #include "GUI/CommonWidgets/DoubleSpinBox.h"
 #include "GUI/Views/SampleDesigner/InterferenceForm.h"
diff --git a/GUI/Views/SampleDesigner/SampleListView.cpp b/GUI/Views/SampleDesigner/SampleListView.cpp
index 0e28df89eaaac43c3c35eb112d31bd5ba1da241e..afcd8b6ca361e70720610e3591d429f82146a8a4 100644
--- a/GUI/Views/SampleDesigner/SampleListView.cpp
+++ b/GUI/Views/SampleDesigner/SampleListView.cpp
@@ -15,7 +15,7 @@
 #include "GUI/Views/SampleDesigner/SampleListView.h"
 #include "GUI/Application/Application.h"
 #include "GUI/Models/Sample/GUIExamplesFactory.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Sample/SampleListModel.h"
 #include "GUI/CommonWidgets/ItemViewOverlayButtons.h"
 #include "GUI/utils/ItemDelegateForHTML.h"
diff --git a/GUI/Views/SampleDesigner/SamplePropertyWidget.cpp b/GUI/Views/SampleDesigner/SamplePropertyWidget.cpp
index c01318f14a37c8d9de2d6c46128ee2c8cbdbc78e..cf46751d20db5142755e940af8d7803657d442b8 100644
--- a/GUI/Views/SampleDesigner/SamplePropertyWidget.cpp
+++ b/GUI/Views/SampleDesigner/SamplePropertyWidget.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/SamplePropertyWidget.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/Views/PropertyEditor/ComponentEditor.h"
 #include <QItemSelection>
 #include <QModelIndexList>
diff --git a/GUI/Views/SampleDesigner/SampleToolBox.cpp b/GUI/Views/SampleDesigner/SampleToolBox.cpp
index 0a18f1d488760e75a5f76cb2fe94a0f05608e935..b03bf6fbc27cf9b745f4a403a9b8ced507cf751e 100644
--- a/GUI/Views/SampleDesigner/SampleToolBox.cpp
+++ b/GUI/Views/SampleDesigner/SampleToolBox.cpp
@@ -14,11 +14,11 @@
 
 #include "GUI/Views/SampleDesigner/SampleToolBox.h"
 #include "GUI/Models/Sample/GUIExamplesFactory.h"
-#include "GUI/Session/ItemCatalog.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/TransformationItem.h"
+#include "GUI/Items/ItemCatalog.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/TransformationItem.h"
 #include "GUI/Views/SampleDesigner/DesignerMimeData.h"
 #include "GUI/Views/SampleDesigner/SampleToolBoxTreeWidget.h"
 #include <QApplication>
diff --git a/GUI/Views/SampleDesigner/SampleTreeWidget.cpp b/GUI/Views/SampleDesigner/SampleTreeWidget.cpp
index f89bb58bfe3b62aa56fc0da70181e96242098c40..f88205f8f8176ad1617a206a10da1e66fd60a0f6 100644
--- a/GUI/Views/SampleDesigner/SampleTreeWidget.cpp
+++ b/GUI/Views/SampleDesigner/SampleTreeWidget.cpp
@@ -14,7 +14,7 @@
 
 #include "GUI/Views/SampleDesigner/SampleTreeWidget.h"
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
-#include "GUI/Session/ItemCatalog.h"
+#include "GUI/Items/ItemCatalog.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Views/SampleDesigner/ItemTreeView.h"
 #include <QAction>
diff --git a/GUI/Views/SampleDesigner/SampleViewAligner.cpp b/GUI/Views/SampleDesigner/SampleViewAligner.cpp
index 2bea50a80faf7f50b4f98591eed9669b920ecf1c..5d778d0cb9f4ccd47147d5454f1299d22eb3529b 100644
--- a/GUI/Views/SampleDesigner/SampleViewAligner.cpp
+++ b/GUI/Views/SampleDesigner/SampleViewAligner.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/SampleViewAligner.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/CommonWidgets/StyleUtils.h"
 #include "GUI/Views/SampleDesigner/DesignerScene.h"
diff --git a/GUI/Views/SampleDesigner/SampleViewFactory.cpp b/GUI/Views/SampleDesigner/SampleViewFactory.cpp
index 96083b480f4b771212b9e4e02685a819d7d4f5aa..e3589b1c3fcb010608f87886db9f36f3461c30a3 100644
--- a/GUI/Views/SampleDesigner/SampleViewFactory.cpp
+++ b/GUI/Views/SampleDesigner/SampleViewFactory.cpp
@@ -13,15 +13,15 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SampleDesigner/SampleViewFactory.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MesoCrystalItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/TransformationItem.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MesoCrystalItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/TransformationItem.h"
 #include "GUI/Views/SampleDesigner/InterferenceViews.h"
 #include "GUI/Views/SampleDesigner/LayerView.h"
 #include "GUI/Views/SampleDesigner/MesoCrystalView.h"
diff --git a/GUI/Views/SampleDesigner/ScriptPanel.cpp b/GUI/Views/SampleDesigner/ScriptPanel.cpp
index 90be281b2eedbc07b88a644694712461a66633c8..84328ebc85684ecfece7c80b691ded421b7870cf 100644
--- a/GUI/Views/SampleDesigner/ScriptPanel.cpp
+++ b/GUI/Views/SampleDesigner/ScriptPanel.cpp
@@ -15,7 +15,7 @@
 #include "GUI/Views/SampleDesigner/ScriptPanel.h"
 #include "Core/Export/ExportToPython.h"
 #include "GUI/Models/Domain/DomainObjectBuilder.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/CommonWidgets/DesignerHelper.h"
 #include "GUI/CommonWidgets/UpdateTimer.h"
diff --git a/GUI/Views/SpecularDataWidgets/SpecularDataCanvas.cpp b/GUI/Views/SpecularDataWidgets/SpecularDataCanvas.cpp
index e976c5c74ddc0f3b0b38eebd568a360a26d719d9..db4903f7a8dbefcabfe53b7d530eb48bf15a9f98 100644
--- a/GUI/Views/SpecularDataWidgets/SpecularDataCanvas.cpp
+++ b/GUI/Views/SpecularDataWidgets/SpecularDataCanvas.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SpecularDataWidgets/SpecularDataCanvas.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/SavePlotAssistant.h"
 #include "GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.h"
 #include "GUI/Project/projectmanager.h"
diff --git a/GUI/Views/SpecularDataWidgets/SpecularDataImportWidget.cpp b/GUI/Views/SpecularDataWidgets/SpecularDataImportWidget.cpp
index f40b42184c271d7176a46daec55e687d9e82b5b8..d1bb3e282297dca914b1ca8de2f505b7c8047a54 100644
--- a/GUI/Views/SpecularDataWidgets/SpecularDataImportWidget.cpp
+++ b/GUI/Views/SpecularDataWidgets/SpecularDataImportWidget.cpp
@@ -15,11 +15,11 @@
 #include "GUI/Views/SpecularDataWidgets/SpecularDataImportWidget.h"
 #include "GUI/DataLoaders/DataLoaderUtil.h"
 #include "GUI/Models/Data/AbstractDataLoaderResultModel.h"
-#include "GUI/Session/DataItemUtils.h"
+#include "GUI/Items/DataItemUtils.h"
 #include "GUI/Models/Data/DataLoaders1D.h"
-#include "GUI/Session/InstrumentItems.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/InstrumentItems.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/mainwindow/mainwindow.h"
 #include "ui_SpecularDataImportWidget.h"
 #include <QAction>
diff --git a/GUI/Views/SpecularDataWidgets/SpecularDataWidget.cpp b/GUI/Views/SpecularDataWidgets/SpecularDataWidget.cpp
index 63359a7df113486aae67335c6bfd51140e81e4ec..ba85b58a8163fa260546dd1d82d3a9f0e4824876 100644
--- a/GUI/Views/SpecularDataWidgets/SpecularDataWidget.cpp
+++ b/GUI/Views/SpecularDataWidgets/SpecularDataWidget.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SpecularDataWidgets/SpecularDataWidget.h"
-#include "GUI/Session/DataItemUtils.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/DataItemUtils.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/IntensityDataPropertyWidget.h"
 #include "GUI/Views/SpecularDataWidgets/SpecularDataCanvas.h"
 #include <QBoxLayout>
diff --git a/GUI/Views/SpecularDataWidgets/SpecularPlot.cpp b/GUI/Views/SpecularDataWidgets/SpecularPlot.cpp
index 3c70cc3cd3d6676e60a32a374e5d361073ed5bf0..f65e3fb396ed9c79895c320f826fdb92dbe92336 100644
--- a/GUI/Views/SpecularDataWidgets/SpecularPlot.cpp
+++ b/GUI/Views/SpecularDataWidgets/SpecularPlot.cpp
@@ -13,8 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SpecularDataWidgets/SpecularPlot.h"
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/CommonWidgets/UpdateTimer.h"
 #include "GUI/Views/IntensityDataWidgets/ColorMapUtils.h"
 #include "GUI/Views/IntensityDataWidgets/PlotEventInfo.h"
diff --git a/GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.cpp b/GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.cpp
index c6754a368834be560ba9890605ad30f89ba1e015..55f66e044c4c3a048466cf8d3c073cb4b7f2089c 100644
--- a/GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.cpp
+++ b/GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/SpecularDataWidgets/SpecularPlotCanvas.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/IntensityDataWidgets/FontScalingEvent.h"
 #include "GUI/Views/IntensityDataWidgets/PlotStatusLabel.h"
 #include "GUI/Views/SpecularDataWidgets/SpecularPlot.h"
diff --git a/GUI/Views/Toplevel/ImportDataView.cpp b/GUI/Views/Toplevel/ImportDataView.cpp
index 583979c1a125b3c314c03fa216c48308cc9b7a55..46b48f4ca15ad235528203e898e5ad5dcada0d40 100644
--- a/GUI/Views/Toplevel/ImportDataView.cpp
+++ b/GUI/Views/Toplevel/ImportDataView.cpp
@@ -13,7 +13,7 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/Toplevel/ImportDataView.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/Views/ImportDataWidgets/RealDataSelectorWidget.h"
 #include "GUI/utils/mainwindow_constants.h"
diff --git a/GUI/Views/Toplevel/SampleView.cpp b/GUI/Views/Toplevel/SampleView.cpp
index 6eb9e8ec2b5aecd3ece354b9e4f7cef2e2526a61..b002a8a164985747baf76abd0b3b3ec31a442c90 100644
--- a/GUI/Views/Toplevel/SampleView.cpp
+++ b/GUI/Views/Toplevel/SampleView.cpp
@@ -15,7 +15,7 @@
 #include "GUI/Views/Toplevel/SampleView.h"
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/Models/Parameter/FilterPropertyProxy.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/CommonWidgets/DocksController.h"
 #include "GUI/Views/SampleDesigner/DesignerScene.h"
 #include "GUI/Views/SampleDesigner/DesignerView.h"
diff --git a/GUI/Views/Toplevel/SimulationView.cpp b/GUI/Views/Toplevel/SimulationView.cpp
index 0bdd9cf0164895d8dc231810da92f46618418ff3..4287d170403fd9c04f449490d16e13cca98c816f 100644
--- a/GUI/Views/Toplevel/SimulationView.cpp
+++ b/GUI/Views/Toplevel/SimulationView.cpp
@@ -15,17 +15,17 @@
 #include "GUI/Views/Toplevel/SimulationView.h"
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/Models/Data/DocumentModel.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Models/Sample/SampleValidator.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "GUI/CommonWidgets/GroupBoxCollapser.h"
 #include "GUI/Views/SimulationWidgets/PythonScriptWidget.h"
 #include "GUI/mainwindow/mainwindow.h"
diff --git a/GUI/Views/Toplevel/TestView.cpp b/GUI/Views/Toplevel/TestView.cpp
index b493893d92cfe96faf3bd68f9bb04369ba3aafbd..8a7a6124243c7d1468e8c132790c4b23fb67c7eb 100644
--- a/GUI/Views/Toplevel/TestView.cpp
+++ b/GUI/Views/Toplevel/TestView.cpp
@@ -13,12 +13,12 @@
 //  ************************************************************************************************
 
 #include "GUI/Views/Toplevel/TestView.h"
-#include "GUI/Session/Data1DViewItem.h"
+#include "GUI/Items/Data1DViewItem.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/MinimizerItem.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/MinimizerItem.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Views/FitWidgets/MinimizerSettingsWidget.h"
 #include "GUI/Views/PropertyEditor/TestComponentView.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceWidget.h"
diff --git a/GUI/mainwindow/LinkInstrumentManager.cpp b/GUI/mainwindow/LinkInstrumentManager.cpp
index d1aded02b66e62ef56abeb17bf603635d0d71b47..c63e5cbf54731f8b57f6605741316f27f8d8f689 100644
--- a/GUI/mainwindow/LinkInstrumentManager.cpp
+++ b/GUI/mainwindow/LinkInstrumentManager.cpp
@@ -13,9 +13,9 @@
 //  ************************************************************************************************
 
 #include "GUI/mainwindow/LinkInstrumentManager.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/Views/ImportDataWidgets/ImportDataUtils.h"
 #include "GUI/mainwindow/mainwindow.h"
diff --git a/GUI/mainwindow/OutputDataIOService.cpp b/GUI/mainwindow/OutputDataIOService.cpp
index 34f4bb8f892cb4a82e4a88eb0c39ae5cc3b043d7..ece8c58392bad49a3b7ba58558f5768f4dc98352 100644
--- a/GUI/mainwindow/OutputDataIOService.cpp
+++ b/GUI/mainwindow/OutputDataIOService.cpp
@@ -14,8 +14,8 @@
 
 #include "GUI/mainwindow/OutputDataIOService.h"
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/ModelPath.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/ModelPath.h"
 #include "GUI/utils/SaveLoadInterface.h"
 #include "GUI/Project/ProjectUtils.h"
 #include "GUI/utils/MessageService.h"
diff --git a/Tests/Functional/GUI/Check.cpp b/Tests/Functional/GUI/Check.cpp
index 71a27cf11d7ace970d472475d5b3cd3b84c1f10c..589313aeee0bdf01a3c2b1a4e952778587a35d45 100644
--- a/Tests/Functional/GUI/Check.cpp
+++ b/Tests/Functional/GUI/Check.cpp
@@ -23,7 +23,7 @@
 #include "GUI/Models/Domain/DomainSimulationBuilder.h"
 #include "GUI/Models/Sample/GUIDomainSampleVisitor.h"
 #include "GUI/Models/Data/GUIObjectBuilder.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Sample/SampleModel.h"
diff --git a/Tests/Unit/GUI/TestAxesItems.cpp b/Tests/Unit/GUI/TestAxesItems.cpp
index 8d4a4b56eb49424c9da63b6ef6ffdfe48bb5e129..843f41e33c7823fc6118735659b64f0be01f488a 100644
--- a/Tests/Unit/GUI/TestAxesItems.cpp
+++ b/Tests/Unit/GUI/TestAxesItems.cpp
@@ -1,9 +1,9 @@
 #include "Base/Axis/FixedBinAxis.h"
 #include "Base/Axis/VariableBinAxis.h"
 #include "Base/Const/Units.h"
-#include "GUI/Session/AxesItems.h"
+#include "GUI/Items/AxesItems.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/PropertyItem.h"
+#include "GUI/Items/PropertyItem.h"
 #include "GUI/Models/Domain/TransformFromDomain.h"
 #include "Tests/GTestWrapper/google_test.h"
 
diff --git a/Tests/Unit/GUI/TestComponentProxyModel.cpp b/Tests/Unit/GUI/TestComponentProxyModel.cpp
index 0f029b8874ba9f4c68df6ecf80dede6830686ca2..d64134355a9ef492d12d31249f44bc170581d608 100644
--- a/Tests/Unit/GUI/TestComponentProxyModel.cpp
+++ b/Tests/Unit/GUI/TestComponentProxyModel.cpp
@@ -1,15 +1,15 @@
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/Mapper/ComponentProxyModel.h"
 #include "GUI/Mapper/ComponentProxyStrategy.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/LayerItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/LayerItem.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include "Tests/Unit/GUI/Utils.h"
 #include <QSignalSpy>
diff --git a/Tests/Unit/GUI/TestComponentUtils.cpp b/Tests/Unit/GUI/TestComponentUtils.cpp
index db33fda0fb81316362049d77b9f62a1b6bf3f306..cfee508bb01040d8028fe6194a56b7b973be740d 100644
--- a/Tests/Unit/GUI/TestComponentUtils.cpp
+++ b/Tests/Unit/GUI/TestComponentUtils.cpp
@@ -1,9 +1,9 @@
 #include "GUI/Mapper/ComponentUtils.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestComponentUtils : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestDataItemViews.cpp b/Tests/Unit/GUI/TestDataItemViews.cpp
index 7cede20c0ac93b6a646c36218dc16e75bd8bf348..bf72686b270c49c88a28fdccd5bec65e13657f76 100644
--- a/Tests/Unit/GUI/TestDataItemViews.cpp
+++ b/Tests/Unit/GUI/TestDataItemViews.cpp
@@ -1,11 +1,11 @@
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/Models/Data/DataProperties.h"
 #include "GUI/Models/Data/DataPropertyContainer.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Data/RealDataModel.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "GUI/Project/projectdocument.h"
 #include "GUI/utils/MessageService.h"
 #include "Tests/GTestWrapper/google_test.h"
diff --git a/Tests/Unit/GUI/TestDataItems.cpp b/Tests/Unit/GUI/TestDataItems.cpp
index ab35a2d3566ad3514ac87a0027b32894c0e291eb..ca22a144d973056cedea2df70259a6ec04120dd4 100644
--- a/Tests/Unit/GUI/TestDataItems.cpp
+++ b/Tests/Unit/GUI/TestDataItems.cpp
@@ -1,6 +1,6 @@
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/SpecularDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/SpecularDataItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QTest>
 
diff --git a/Tests/Unit/GUI/TestDetectorItems.cpp b/Tests/Unit/GUI/TestDetectorItems.cpp
index 19ae7207f4f2c9d6442cf7546a37cfaaef342fa1..9531816ab65018fb34106f0f0b39ba3366c29296 100644
--- a/Tests/Unit/GUI/TestDetectorItems.cpp
+++ b/Tests/Unit/GUI/TestDetectorItems.cpp
@@ -3,11 +3,11 @@
 #include "Device/Resolution/ConvolutionDetectorResolution.h"
 #include "Device/Resolution/ResolutionFunction2DGaussian.h"
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/RectangularDetectorItem.h"
-#include "GUI/Session/ResolutionFunctionItems.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/RectangularDetectorItem.h"
+#include "GUI/Items/ResolutionFunctionItems.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestDetectorItems : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestFTDistributionItems.cpp b/Tests/Unit/GUI/TestFTDistributionItems.cpp
index 18b811b2da7a8bfbc80ea940eda903f4de37eee7..d4348bcd96fd4b2fb68511f5f6adf46d53a37d37 100644
--- a/Tests/Unit/GUI/TestFTDistributionItems.cpp
+++ b/Tests/Unit/GUI/TestFTDistributionItems.cpp
@@ -1,4 +1,4 @@
-#include "GUI/Session/FTDistributionItems.h"
+#include "GUI/Items/FTDistributionItems.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestFTDistributionItems : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestFitParameterModel.cpp b/Tests/Unit/GUI/TestFitParameterModel.cpp
index 1f4c3c5766b8a108f1b797572a87e976dcd9b829..ddfe77e2a71cb4a4fc772afb361e7252462f5301 100644
--- a/Tests/Unit/GUI/TestFitParameterModel.cpp
+++ b/Tests/Unit/GUI/TestFitParameterModel.cpp
@@ -1,6 +1,6 @@
-#include "GUI/Session/FitParameterItems.h"
+#include "GUI/Items/FitParameterItems.h"
 #include "GUI/Models/Fit/FitParameterProxyModel.h"
-#include "GUI/Session/FitSuiteItem.h"
+#include "GUI/Items/FitSuiteItem.h"
 #include "GUI/Models/Job/JobModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 
diff --git a/Tests/Unit/GUI/TestFormFactorItems.cpp b/Tests/Unit/GUI/TestFormFactorItems.cpp
index 7cd231905cbbdaa1172af42b83c002915bc24618..e0ee129bdaab3409c63ef94bbaf2e161540ad21e 100644
--- a/Tests/Unit/GUI/TestFormFactorItems.cpp
+++ b/Tests/Unit/GUI/TestFormFactorItems.cpp
@@ -1,6 +1,6 @@
 #include "Base/Const/Units.h"
 #include "Base/Utils/Algorithms.h"
-#include "GUI/Session/FormFactorItems.h"
+#include "GUI/Items/FormFactorItems.h"
 #include "Sample/HardParticle/FormFactorAnisoPyramid.h"
 #include "Tests/GTestWrapper/google_test.h"
 
diff --git a/Tests/Unit/GUI/TestGUICoreObjectCorrespondence.cpp b/Tests/Unit/GUI/TestGUICoreObjectCorrespondence.cpp
index d9148637a227bf7e50560b77454abd522f8e416c..ccfe88a3ec9297c9c6db2322d3897e16bc444735 100644
--- a/Tests/Unit/GUI/TestGUICoreObjectCorrespondence.cpp
+++ b/Tests/Unit/GUI/TestGUICoreObjectCorrespondence.cpp
@@ -1,6 +1,6 @@
 #include "Base/Const/Units.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/InterferenceItems.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/InterferenceItems.h"
 #include "Sample/Aggregate/Interferences.h"
 #include "Sample/HardParticle/HardParticles.h"
 #include "Tests/GTestWrapper/google_test.h"
diff --git a/Tests/Unit/GUI/TestGroupItem.cpp b/Tests/Unit/GUI/TestGroupItem.cpp
index 64b9cae01eeba525f271a4d56cb27b11c1695c0f..2179a8dbf0244913014343f4f6bde8bb1fab4114 100644
--- a/Tests/Unit/GUI/TestGroupItem.cpp
+++ b/Tests/Unit/GUI/TestGroupItem.cpp
@@ -1,10 +1,10 @@
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/DistributionItems.h"
+#include "GUI/Items/DistributionItems.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include "Tests/Unit/GUI/Utils.h"
 
diff --git a/Tests/Unit/GUI/TestInstrumentModel.cpp b/Tests/Unit/GUI/TestInstrumentModel.cpp
index b7c89c45d6e3d53fbd0a2aa06b97cdc7e6233bfb..8c3b7df685fd7903448f1add8b53c61cbd689274 100644
--- a/Tests/Unit/GUI/TestInstrumentModel.cpp
+++ b/Tests/Unit/GUI/TestInstrumentModel.cpp
@@ -1,4 +1,4 @@
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QSignalSpy>
diff --git a/Tests/Unit/GUI/TestLayerItems.cpp b/Tests/Unit/GUI/TestLayerItems.cpp
index 4769f949008b10553858e346a55c265bd8c87283..c452bc8a8d18b12dfccecd2fe2f5a268e2fca241 100644
--- a/Tests/Unit/GUI/TestLayerItems.cpp
+++ b/Tests/Unit/GUI/TestLayerItems.cpp
@@ -1,6 +1,6 @@
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MaterialItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MaterialItem.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "Tests/GTestWrapper/google_test.h"
diff --git a/Tests/Unit/GUI/TestLayerRoughnessItems.cpp b/Tests/Unit/GUI/TestLayerRoughnessItems.cpp
index 16faf6c8b25f7ed0bed9438cde80a7b542e769c7..9dddab7f2521fdc3984bcbdaaaca85e920c3ce38 100644
--- a/Tests/Unit/GUI/TestLayerRoughnessItems.cpp
+++ b/Tests/Unit/GUI/TestLayerRoughnessItems.cpp
@@ -1,5 +1,5 @@
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/LayerRoughnessItems.h"
+#include "GUI/Items/LayerRoughnessItems.h"
 #include "GUI/Models/Domain/TransformFromDomain.h"
 #include "GUI/Models/Domain/TransformToDomain.h"
 #include "Tests/GTestWrapper/google_test.h"
diff --git a/Tests/Unit/GUI/TestLinkInstrument.cpp b/Tests/Unit/GUI/TestLinkInstrument.cpp
index 9802824e563ed69e6e0da8464d8e98696eb53749..39f7a0dd785a7b420dc4571be9e7531a05dd8159 100644
--- a/Tests/Unit/GUI/TestLinkInstrument.cpp
+++ b/Tests/Unit/GUI/TestLinkInstrument.cpp
@@ -1,10 +1,10 @@
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
-#include "GUI/Session/RectangularDetectorItem.h"
+#include "GUI/Items/RectangularDetectorItem.h"
 #include "GUI/Project/projectdocument.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include "Tests/Unit/GUI/Utils.h"
diff --git a/Tests/Unit/GUI/TestMapperCases.cpp b/Tests/Unit/GUI/TestMapperCases.cpp
index 90bd4b5512b070736b5b4b5e913238e45f5ab07f..6460808b06dff619985604e54151bac826a15782 100644
--- a/Tests/Unit/GUI/TestMapperCases.cpp
+++ b/Tests/Unit/GUI/TestMapperCases.cpp
@@ -1,13 +1,13 @@
 #include "GUI/Models/Group/ComboProperty.h"
 #include "GUI/Models/Data/DocumentModel.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SimulationOptionsItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SimulationOptionsItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QtTest>
 
diff --git a/Tests/Unit/GUI/TestMapperForItem.cpp b/Tests/Unit/GUI/TestMapperForItem.cpp
index 1364d190a511ac78af8ba67cb48675e3770228cb..f8771dbbe0bb0c886cdaab9a32fd592dd537d045 100644
--- a/Tests/Unit/GUI/TestMapperForItem.cpp
+++ b/Tests/Unit/GUI/TestMapperForItem.cpp
@@ -1,10 +1,10 @@
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MaskItems.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ProjectionItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MaskItems.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ProjectionItems.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <memory>
 
diff --git a/Tests/Unit/GUI/TestMaterialModel.cpp b/Tests/Unit/GUI/TestMaterialModel.cpp
index 80ef7f269910e01d5193dfaed129956c1cdc66bd..f5ee04a81d324e3e9131568bc9c27c2568f5c674 100644
--- a/Tests/Unit/GUI/TestMaterialModel.cpp
+++ b/Tests/Unit/GUI/TestMaterialModel.cpp
@@ -1,5 +1,5 @@
-#include "GUI/Session/MaterialDataItems.h"
-#include "GUI/Session/MaterialItemUtils.h"
+#include "GUI/Items/MaterialDataItems.h"
+#include "GUI/Items/MaterialItemUtils.h"
 #include "GUI/Models/Material/MaterialModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <memory>
diff --git a/Tests/Unit/GUI/TestModelUtils.cpp b/Tests/Unit/GUI/TestModelUtils.cpp
index 93f4c499665484d964b3677c97d6162e7e3ab571..ad343475edfefb287aa1bc99c9033f5f1c3a98db 100644
--- a/Tests/Unit/GUI/TestModelUtils.cpp
+++ b/Tests/Unit/GUI/TestModelUtils.cpp
@@ -1,8 +1,8 @@
-#include "GUI/Session/LayerItem.h"
+#include "GUI/Items/LayerItem.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QVector>
 
diff --git a/Tests/Unit/GUI/TestMultiLayerItem.cpp b/Tests/Unit/GUI/TestMultiLayerItem.cpp
index 4f3f85f2ffb43a41875ead5165ce61fd151a704a..1e84195ea3d1cad9f5d778df2f7b8643c52396b7 100644
--- a/Tests/Unit/GUI/TestMultiLayerItem.cpp
+++ b/Tests/Unit/GUI/TestMultiLayerItem.cpp
@@ -1,7 +1,7 @@
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/LayerRoughnessItems.h"
-#include "GUI/Session/MultiLayerItem.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/LayerRoughnessItems.h"
+#include "GUI/Items/MultiLayerItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 
diff --git a/Tests/Unit/GUI/TestOutputDataIOService.cpp b/Tests/Unit/GUI/TestOutputDataIOService.cpp
index 96bd8376b7465b6eb67e9055e07b7c94221c10ee..317a17a788173a0acda43ae77a2bac553657f5ff 100644
--- a/Tests/Unit/GUI/TestOutputDataIOService.cpp
+++ b/Tests/Unit/GUI/TestOutputDataIOService.cpp
@@ -1,14 +1,14 @@
 #include "Device/Histo/IntensityDataIOFactory.h"
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/utils/Error.h"
 #include "GUI/Models/Data/ImportDataInfo.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItem.h"
-#include "GUI/Session/JobItemUtils.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItem.h"
+#include "GUI/Items/JobItemUtils.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/JobModelFunctions.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/JobModelFunctions.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/mainwindow/OutputDataIOService.h"
 #include "GUI/Project/ProjectUtils.h"
diff --git a/Tests/Unit/GUI/TestParaCrystalItems.cpp b/Tests/Unit/GUI/TestParaCrystalItems.cpp
index b7093704c2acadc622727c42c96907db8cff52ad..a43f6ed5ebc5f17d5a81a0f35ab37e95f9425af3 100644
--- a/Tests/Unit/GUI/TestParaCrystalItems.cpp
+++ b/Tests/Unit/GUI/TestParaCrystalItems.cpp
@@ -1,10 +1,10 @@
 #include "Base/Const/Units.h"
-#include "GUI/Session/FTDistributionItems.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/Lattice2DItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/FTDistributionItems.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/Lattice2DItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Models/Domain/TransformFromDomain.h"
 #include "Sample/Aggregate/Interference2DParaCrystal.h"
diff --git a/Tests/Unit/GUI/TestParticleCoreShell.cpp b/Tests/Unit/GUI/TestParticleCoreShell.cpp
index 96039724b181a4d1399143d3459b6d2b1dfcc524..f1e4e2726e22ee2e8c71dcc98ec2f1f264affacc 100644
--- a/Tests/Unit/GUI/TestParticleCoreShell.cpp
+++ b/Tests/Unit/GUI/TestParticleCoreShell.cpp
@@ -1,10 +1,10 @@
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleCoreShellItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleCoreShellItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QtTest>
 
diff --git a/Tests/Unit/GUI/TestParticleItem.cpp b/Tests/Unit/GUI/TestParticleItem.cpp
index beae903623bed2cc06a05c36d118bb6250c14dc0..389f3a51c71831b3bf32f1f5272668c26d90595c 100644
--- a/Tests/Unit/GUI/TestParticleItem.cpp
+++ b/Tests/Unit/GUI/TestParticleItem.cpp
@@ -1,9 +1,9 @@
 #include "GUI/Models/Types/DoubleDescriptor.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/ParticleCompositionItem.h"
-#include "GUI/Session/ParticleItem.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/ParticleCompositionItem.h"
+#include "GUI/Items/ParticleItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 using namespace GUI::Session::ItemUtils;
diff --git a/Tests/Unit/GUI/TestParticleLayoutItem.h b/Tests/Unit/GUI/TestParticleLayoutItem.h
index e8f5be77fc5cbe86d65cd7dbc81dd25a47d9de4e..c5d72a2a66c351da34a72cdfc93b0d84ecdf12d3 100644
--- a/Tests/Unit/GUI/TestParticleLayoutItem.h
+++ b/Tests/Unit/GUI/TestParticleLayoutItem.h
@@ -2,11 +2,11 @@
 #define BORNAGAIN_TESTS_UNIT_GUI_TESTPARTICLELAYOUTITEM_H
 
 #include "Base/Math/Constants.h"
-#include "GUI/Session/InterferenceItems.h"
-#include "GUI/Session/Lattice2DItems.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/InterferenceItems.h"
+#include "GUI/Items/Lattice2DItems.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemUtils.h"
+#include "GUI/Items/SessionItemUtils.h"
 #include "Tests/Unit/utilities/google_test.h"
 
 class TestParticleLayoutItem : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestProjectDocument.cpp b/Tests/Unit/GUI/TestProjectDocument.cpp
index ea72be15e073dabc3b38811a18236072a7fe8999..0912012fd404b6ae57d994d22eacde1a5a5d9e9a 100644
--- a/Tests/Unit/GUI/TestProjectDocument.cpp
+++ b/Tests/Unit/GUI/TestProjectDocument.cpp
@@ -1,9 +1,9 @@
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/Project/ProjectUtils.h"
 #include "GUI/Project/projectdocument.h"
diff --git a/Tests/Unit/GUI/TestProjectUtils.cpp b/Tests/Unit/GUI/TestProjectUtils.cpp
index 40995528edee80468fb42ac5c5f2c55f3bbc6e43..4b7ba6c0d8294ff28ba97fa5f6f2978f5f0e4f74 100644
--- a/Tests/Unit/GUI/TestProjectUtils.cpp
+++ b/Tests/Unit/GUI/TestProjectUtils.cpp
@@ -1,5 +1,5 @@
 #include "GUI/utils/Error.h"
-#include "GUI/Session/ItemFileNameUtils.h"
+#include "GUI/Items/ItemFileNameUtils.h"
 #include "GUI/Project/ProjectUtils.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include "Utils.h"
diff --git a/Tests/Unit/GUI/TestPropertyRepeater.cpp b/Tests/Unit/GUI/TestPropertyRepeater.cpp
index e6c2bc746529da9d6448bebd86e71a3599b1753f..3c7efed522f0071dd5a6f2a13a2901c4845a2f59 100644
--- a/Tests/Unit/GUI/TestPropertyRepeater.cpp
+++ b/Tests/Unit/GUI/TestPropertyRepeater.cpp
@@ -1,6 +1,6 @@
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Views/IntensityDataWidgets/PropertyRepeater.h"
 #include "Tests/GTestWrapper/google_test.h"
 
diff --git a/Tests/Unit/GUI/TestProxyModelStrategy.cpp b/Tests/Unit/GUI/TestProxyModelStrategy.cpp
index 861fab9bbfdcfec37224ada9431f413c58a49dd5..0dea3e35049b2e9e8a9bd7dcbd19544b387bc2b0 100644
--- a/Tests/Unit/GUI/TestProxyModelStrategy.cpp
+++ b/Tests/Unit/GUI/TestProxyModelStrategy.cpp
@@ -1,12 +1,12 @@
 #include "GUI/Mapper/ComponentProxyModel.h"
 #include "GUI/Mapper/ComponentProxyStrategy.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/GroupItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/GroupItem.h"
 #include "GUI/Mapper/ModelUtils.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestProxyModelStrategy : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestRealDataModel.cpp b/Tests/Unit/GUI/TestRealDataModel.cpp
index 666685240eb4eb39e8825244136a9b53344616f4..8475798bf9a2d6358d4727b4061f8f1d7278e81b 100644
--- a/Tests/Unit/GUI/TestRealDataModel.cpp
+++ b/Tests/Unit/GUI/TestRealDataModel.cpp
@@ -1,6 +1,6 @@
 #include "Base/Axis/PointwiseAxis.h"
-#include "GUI/Session/DataItem.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/DataItem.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QSignalSpy>
diff --git a/Tests/Unit/GUI/TestRealSpaceBuilderUtils.cpp b/Tests/Unit/GUI/TestRealSpaceBuilderUtils.cpp
index 7b5ee87080d3fd4f0db9e0447d2f75518d5d4c49..63bb0df7ac2dca46587bdcd883e8a21bc1aa3b62 100644
--- a/Tests/Unit/GUI/TestRealSpaceBuilderUtils.cpp
+++ b/Tests/Unit/GUI/TestRealSpaceBuilderUtils.cpp
@@ -1,7 +1,7 @@
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/ParticleLayoutItem.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/ParticleLayoutItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
 #include "GUI/Views/RealSpaceWidgets/Particle3DContainer.h"
 #include "GUI/Views/RealSpaceWidgets/RealSpaceBuilder.h"
diff --git a/Tests/Unit/GUI/TestSaveService.cpp b/Tests/Unit/GUI/TestSaveService.cpp
index 8464866947c0088be83bfe7fdb1c4921a49b5b8a..ca07130f5311d445f4b3e5920e9f8f1133a3052c 100644
--- a/Tests/Unit/GUI/TestSaveService.cpp
+++ b/Tests/Unit/GUI/TestSaveService.cpp
@@ -1,10 +1,10 @@
 #include "GUI/Models/Data/ApplicationModels.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/JobItemUtils.h"
-#include "GUI/Session/RealDataItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/JobItemUtils.h"
+#include "GUI/Items/RealDataItem.h"
 #include "GUI/Models/Data/RealDataModel.h"
 #include "GUI/mainwindow/AutosaveController.h"
 #include "GUI/Project/ProjectUtils.h"
diff --git a/Tests/Unit/GUI/TestSavingSpecularData.cpp b/Tests/Unit/GUI/TestSavingSpecularData.cpp
index 9a95a8fd860b267e1e6415d05a9a84330a8cd9ee..6bd8ed46b6c7d5f03a26fb11d7b79c0064dc68aa 100644
--- a/Tests/Unit/GUI/TestSavingSpecularData.cpp
+++ b/Tests/Unit/GUI/TestSavingSpecularData.cpp
@@ -1,18 +1,18 @@
 #include "Base/Axis/PointwiseAxis.h"
 #include "Device/Histo/IntensityDataIOFactory.h"
 #include "GUI/Models/Data/ApplicationModels.h"
-#include "GUI/Session/DataItem.h"
+#include "GUI/Items/DataItem.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/GroupItem.h"
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/GroupItem.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/IntensityDataItem.h"
-#include "GUI/Session/ItemFileNameUtils.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/IntensityDataItem.h"
+#include "GUI/Items/ItemFileNameUtils.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/JobModelFunctions.h"
-#include "GUI/Session/PointwiseAxisItem.h"
-#include "GUI/Session/SpecularBeamInclinationItem.h"
+#include "GUI/Items/JobModelFunctions.h"
+#include "GUI/Items/PointwiseAxisItem.h"
+#include "GUI/Items/SpecularBeamInclinationItem.h"
 #include "GUI/mainwindow/OutputDataIOService.h"
 #include "GUI/Project/ProjectUtils.h"
 #include "Tests/GTestWrapper/google_test.h"
diff --git a/Tests/Unit/GUI/TestSessionItem.cpp b/Tests/Unit/GUI/TestSessionItem.cpp
index 41eb455147946f8329153115ae20fbebd1f5bf50..27dd9346c5ca34d070e7471dc2523615dbc75d8d 100644
--- a/Tests/Unit/GUI/TestSessionItem.cpp
+++ b/Tests/Unit/GUI/TestSessionItem.cpp
@@ -1,4 +1,4 @@
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/SessionModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 #define EXPECT_ASSERT_TRIGGERED(condition) EXPECT_THROW((condition), std::runtime_error)
diff --git a/Tests/Unit/GUI/TestSessionItemController.cpp b/Tests/Unit/GUI/TestSessionItemController.cpp
index 8f557cfc94261542e77157fa715d816b731aa128..248e4286dce823e3c7bddc025ccf3c2bf3cb1910 100644
--- a/Tests/Unit/GUI/TestSessionItemController.cpp
+++ b/Tests/Unit/GUI/TestSessionItemController.cpp
@@ -1,5 +1,5 @@
-#include "GUI/Session/AxesItems.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/AxesItems.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/CommonWidgets/SessionItemController.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include "Tests/Unit/GUI/TestSessionItemControllerHelper.h"
diff --git a/Tests/Unit/GUI/TestSessionItemControllerHelper.cpp b/Tests/Unit/GUI/TestSessionItemControllerHelper.cpp
index ee84216c1ad80677971dfb8351be1306b6e6d355..3d77d894f4bd312605e5dd67ea2c8755d319fb92 100644
--- a/Tests/Unit/GUI/TestSessionItemControllerHelper.cpp
+++ b/Tests/Unit/GUI/TestSessionItemControllerHelper.cpp
@@ -1,5 +1,5 @@
 #include "Tests/Unit/GUI/TestSessionItemControllerHelper.h"
-#include "GUI/Session/SessionItem.h"
+#include "GUI/Items/SessionItem.h"
 #include "GUI/CommonWidgets/SessionItemController.h"
 
 TestListener::TestListener()
diff --git a/Tests/Unit/GUI/TestSessionItemData.cpp b/Tests/Unit/GUI/TestSessionItemData.cpp
index 722c6f7c16afe4015278ccf42d32a909b54982b8..2d9e485094e184e5abe1a9816772542767a4ec7a 100644
--- a/Tests/Unit/GUI/TestSessionItemData.cpp
+++ b/Tests/Unit/GUI/TestSessionItemData.cpp
@@ -1,5 +1,5 @@
-#include "GUI/Session/SessionFlags.h"
-#include "GUI/Session/SessionItemData.h"
+#include "GUI/Items/SessionFlags.h"
+#include "GUI/Items/SessionItemData.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestSessionItemData : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestSessionItemTags.cpp b/Tests/Unit/GUI/TestSessionItemTags.cpp
index 50f0e9bfe383f6bda6518376eae7dc7137879255..aea9cd80f9053c2719a3698ee24ee416793f5048 100644
--- a/Tests/Unit/GUI/TestSessionItemTags.cpp
+++ b/Tests/Unit/GUI/TestSessionItemTags.cpp
@@ -1,7 +1,7 @@
 #include "GUI/utils/Error.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/SessionItemTags.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/SessionItemTags.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestSessionItemTags : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestSessionItemUtils.cpp b/Tests/Unit/GUI/TestSessionItemUtils.cpp
index 12837c51516b297431fd12e99312fa4dbbe088dc..a785819f5a9ca60b28a0cc714b0690f5b96b0d16 100644
--- a/Tests/Unit/GUI/TestSessionItemUtils.cpp
+++ b/Tests/Unit/GUI/TestSessionItemUtils.cpp
@@ -1,8 +1,8 @@
 #include "GUI/Models/Group/ComboProperty.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionItemUtils.h"
-#include "GUI/Session/SessionModel.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionItemUtils.h"
+#include "GUI/Items/SessionModel.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 class TestSessionItemUtils : public ::testing::Test {
diff --git a/Tests/Unit/GUI/TestSessionModel.cpp b/Tests/Unit/GUI/TestSessionModel.cpp
index 2bc4e18630ca5ada29b069711930f64e54279f76..4a8a9695ed185070e0f12b317e704ee7764faa6e 100644
--- a/Tests/Unit/GUI/TestSessionModel.cpp
+++ b/Tests/Unit/GUI/TestSessionModel.cpp
@@ -1,15 +1,15 @@
-#include "GUI/Session/InstrumentItems.h"
+#include "GUI/Items/InstrumentItems.h"
 #include "GUI/Models/Instrument/InstrumentModel.h"
-#include "GUI/Session/JobItem.h"
+#include "GUI/Items/JobItem.h"
 #include "GUI/Models/Job/JobModel.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MaskItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MaskItems.h"
 #include "GUI/Models/Material/MaterialModel.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/PropertyItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/PropertyItem.h"
 #include "GUI/Models/Sample/SampleModel.h"
-#include "GUI/Session/SessionItemTags.h"
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/SessionItemTags.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QSignalSpy>
 #include <QXmlStreamWriter>
diff --git a/Tests/Unit/GUI/TestSessionXML.cpp b/Tests/Unit/GUI/TestSessionXML.cpp
index 7b7ce9423d54b5e761cfea54dd6bb41fb0d35122..7ee674678a5b0110fdd26358d9e3ed921003ec8b 100644
--- a/Tests/Unit/GUI/TestSessionXML.cpp
+++ b/Tests/Unit/GUI/TestSessionXML.cpp
@@ -1,9 +1,9 @@
-#include "GUI/Session/FormFactorItems.h"
-#include "GUI/Session/LayerItem.h"
-#include "GUI/Session/MultiLayerItem.h"
-#include "GUI/Session/ParticleItem.h"
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/FormFactorItems.h"
+#include "GUI/Items/LayerItem.h"
+#include "GUI/Items/MultiLayerItem.h"
+#include "GUI/Items/ParticleItem.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "Tests/GTestWrapper/google_test.h"
 #include <QXmlStreamReader>
 #include <QXmlStreamWriter>
diff --git a/Tests/Unit/GUI/TestVectorItem.cpp b/Tests/Unit/GUI/TestVectorItem.cpp
index 81e1d31a5859a4a3d224b9ff04fb1d3bcd0a202d..51873c9cbdd6af760b2d31a50967807e83f65ad1 100644
--- a/Tests/Unit/GUI/TestVectorItem.cpp
+++ b/Tests/Unit/GUI/TestVectorItem.cpp
@@ -1,4 +1,4 @@
-#include "GUI/Session/VectorItem.h"
+#include "GUI/Items/VectorItem.h"
 #include "Tests/GTestWrapper/google_test.h"
 
 //! Tests VectorItem class.
diff --git a/Tests/Unit/GUI/Utils.cpp b/Tests/Unit/GUI/Utils.cpp
index b09af7bfb67f41cf3b863e2c41f2763b190aebbb..8001678d5c2b549cb5235b12ed41c903365f3d15 100644
--- a/Tests/Unit/GUI/Utils.cpp
+++ b/Tests/Unit/GUI/Utils.cpp
@@ -17,8 +17,8 @@
 #include "Device/Data/DataUtils.h"
 #include "Device/Histo/IntensityDataIOFactory.h"
 #include "GUI/utils/Error.h"
-#include "GUI/Session/RealDataItem.h"
-#include "GUI/Session/SessionModel.h"
+#include "GUI/Items/RealDataItem.h"
+#include "GUI/Items/SessionModel.h"
 #include "GUI/Project/ProjectUtils.h"
 #include <QDir>
 
diff --git a/Tests/Unit/GUI/Utils.h b/Tests/Unit/GUI/Utils.h
index 147be7ab6ff7c0be5d5ee54368ede153015e9b63..29e4a3ba47838acf129e0f049435a23fbaa901df 100644
--- a/Tests/Unit/GUI/Utils.h
+++ b/Tests/Unit/GUI/Utils.h
@@ -16,8 +16,8 @@
 #ifndef BORNAGAIN_TESTS_UNIT_GUI_UTILS_H
 #define BORNAGAIN_TESTS_UNIT_GUI_UTILS_H
 
-#include "GUI/Session/PropertyItem.h"
-#include "GUI/Session/SessionXML.h"
+#include "GUI/Items/PropertyItem.h"
+#include "GUI/Items/SessionXML.h"
 #include <QString>
 #include <QXmlStreamWriter>