diff --git a/app/Main.hs b/app/Main.hs
index e04946e..b6fb628 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -114,11 +114,11 @@ main = do
   uiGrid <- GTK.gridNew
   GTK.setContainerChild baseOverlay uiGrid
 
-  logo      <- GTK.boxNew   GTK.OrientationVertical   0
-  titleBar  <- GTK.boxNew   GTK.OrientationHorizontal 0
-  toolBar   <- GTK.boxNew   GTK.OrientationVertical   0
-  mainPane  <- GTK.panedNew GTK.OrientationHorizontal
-  panelGrid <- GTK.gridNew
+  logo     <- GTK.boxNew   GTK.OrientationVertical   0
+  titleBar <- GTK.boxNew   GTK.OrientationHorizontal 0
+  toolBar  <- GTK.boxNew   GTK.OrientationVertical   0
+  mainPane <- GTK.panedNew GTK.OrientationHorizontal
+  panelBox <- GTK.boxNew   GTK.OrientationVertical   0
 
   GTK.gridAttach uiGrid logo      0 0 1 2
   GTK.gridAttach uiGrid titleBar  1 0 2 1
@@ -127,8 +127,8 @@ main = do
 
   mainView     <- GTK.boxNew GTK.OrientationVertical   0
 
-  GTK.panedPack1 mainPane mainView  True  False
-  GTK.panedPack2 mainPane panelGrid False False
+  GTK.panedPack1 mainPane mainView True  False
+  GTK.panedPack2 mainPane panelBox False False
 
   fileBar      <- GTK.scrolledWindowNew ( Nothing @GTK.Adjustment ) ( Nothing @GTK.Adjustment )
   viewportGrid <- GTK.gridNew
@@ -420,7 +420,55 @@ main = do
   ---------------------------------------------------------
   -- Panels
 
-  widgetAddClass panelGrid "panels"
+  widgetAddClass panelBox "panels"
+
+  pane1 <- GTK.panedNew GTK.OrientationVertical
+  GTK.boxPackStart panelBox pane1 True True 0
+
+  panels1 <- GTK.notebookNew
+  panels2 <- GTK.notebookNew
+
+  GTK.notebookSetGroupName panels1 ( Just "Panel" )
+  GTK.notebookSetGroupName panels2 ( Just "Panel" )
+
+  GTK.panedPack1 pane1 panels1 True True
+  GTK.panedPack2 pane1 panels2 True True
+
+  strokesPanel   <- GTK.boxNew GTK.OrientationVertical 0
+  brushesPanel   <- GTK.boxNew GTK.OrientationVertical 0
+  transformPanel <- GTK.boxNew GTK.OrientationVertical 0
+
+  strokesTab   <- GTK.labelNew ( Just "Strokes" )
+  brushesTab   <- GTK.labelNew ( Just "Brushes" )
+  transformTab <- GTK.labelNew ( Just "Transform" )
+
+  for_ [ strokesTab, brushesTab, transformTab ] \ tab -> do
+    widgetAddClasses tab [ "plain", "text", "panelTab" ]
+
+  for_ [ strokesPanel, brushesPanel, transformPanel ] \ panel -> do
+    widgetAddClass panel "panel"
+
+  void $ GTK.notebookAppendPage panels1   strokesPanel ( Just   strokesTab )
+  void $ GTK.notebookAppendPage panels1   brushesPanel ( Just   brushesTab )
+
+  void $ GTK.notebookAppendPage panels2 transformPanel ( Just transformTab )
+
+  GTK.notebookSetTabReorderable panels1   strokesPanel True
+  GTK.notebookSetTabDetachable  panels1   strokesPanel True
+  GTK.notebookSetTabReorderable panels1   brushesPanel True
+  GTK.notebookSetTabDetachable  panels1   brushesPanel True
+
+  GTK.notebookSetTabReorderable panels2 transformPanel True
+  GTK.notebookSetTabDetachable  panels2 transformPanel True
+
+  strokesContent   <- GTK.labelNew ( Just "Strokes tab content..." )
+  brushesContent   <- GTK.labelNew ( Just "Brushes tab content..." )
+  transformContent <- GTK.labelNew ( Just "Transform tab content..." )
+
+  GTK.boxPackStart   strokesPanel   strokesContent True True 0
+  GTK.boxPackStart   brushesPanel   brushesContent True True 0
+  GTK.boxPackStart transformPanel transformContent True True 0
+
 
   ---------------------------------------------------------
   -- Info bar
diff --git a/assets/theme.css b/assets/theme.css
index 9907f40..c5d37e1 100644
--- a/assets/theme.css
+++ b/assets/theme.css
@@ -319,6 +319,25 @@ tooltip {
   font-size: 12px;
 }
 
+.panels tab {
+  padding-left: 6px;
+  padding-right: 6px;
+  border-top: 2px solid rgb(41, 40, 40);
+}
+
+.panels tab:hover {
+  border-color: rgb(72,70,61);
+}
+
+.panels tab:active, .panels tab:checked {
+  background-color: rgb(72,70,61);
+  border-color: rgb(234,223,204);
+}
+
+.panel {
+  background-color: rgb(72,70,61);
+}
+
 /* Info bar */
 .infoBar {
   min-height: 40px;