diff --git a/src/graph_ZCA/app.py b/src/graph_ZCA/app.py
--- a/src/graph_ZCA/app.py
+++ b/src/graph_ZCA/app.py
@@ -1,63 +1,79 @@
+# Here starts the boiler plate
+from zope.interface import implements   # <- this is needed here to form the PlotImage component
+from zope.component import getGlobalSiteManager, adapts   # <- Only needed for the extension afterwards
+gsm = getGlobalSiteManager()                              # <- Only needed for the extension afterwards
+# End of Boiler plate
 
-from zope.interface import implements
+# Import of the sub components.
+from graph_ZCA.components import BaseComponent, Image, Axis, ViewBox
 
-from graph_ZCA.components import BaseComponent, Image, Axis, AxisComponent, ViewBox, TickLabelComponent
+# Only needed for the extension afterwards.
 from graph_ZCA.interfaces import IAxis, IViewBox, IBaseComponent
-
-from zope.component import getGlobalSiteManager, adapts
-
-gsm = getGlobalSiteManager()
+from graph_ZCA.components import TickLabelComponent, AxisComponent
 
 
+# Set up a new interface for the component PlotImage. Here usually properties, functions and other exposed items
+# of a PlotImage instance would be documented and registered to the framework. Since the only function render is
+# already documented for IBaseComponent nothing has to be done here.
 class IPlotImage(IBaseComponent):
     """
     Component to plot a 2d graph of a given image
     """
 
-
+# Here the component itself is constructed. The component inherits from a simple BaseComponent without much importance.
+# The only crucial requirement is that every component knows its parent component as self.parent, which is the first
+# parameter to the constructor. The top most component has a parent of NONE.
 class PlotImage( BaseComponent):
     """
     Makes a 2D plot for an image
     """
-    implements(IPlotImage)
+    implements(IPlotImage)   # here the interface specified above is used.
 
     def __init__(self, parent):
-        super(PlotImage, self).__init__(parent)
+        super(PlotImage, self).__init__(parent)   # tribute to the super class
 
-        self.vb = ViewBox(self)()
+        self.vb = ViewBox(self)()   # make a ViewBox. Please notice the double Braces. These are neccessary for the framework.
+                                    # In fact here in no instance generated but a factory. And with the second brace
+                                    # the factory produces the instance.
+                                    # The PlotImage "self" is assigned as parent for the ViewBox
 
-        x_axis = Axis(self.vb)()
+        x_axis = Axis(self.vb)()    # Same pattern here
+                                    # The axis are assigned to the viewbox
         x_axis.orientation='bottom'
         x_axis.start=0
         x_axis.end=8
 
-        y_axis = Axis(self.vb)()
+        y_axis = Axis(self.vb)()    # and here
         y_axis.orientation='left'
         y_axis.start=-5
         y_axis.end=3
 
 
-        self.vb.addItem( x_axis )
+        self.vb.addItem( x_axis )   # Finally the axis are given to the viewbox. This step may be not necessary and
+                                    # may be done automatically while assigning the parent to the axis.
         self.vb.addItem( y_axis )
 
-    def render(self):
+    def render(self):               # In this prototype code every component optains a render method that is used to generate
+                                    # some simple output
         return self.vb.render()
 
 
-class NewAxisComponent(AxisComponent):
-    adapts(IViewBox)
-
-gsm.registerAdapter(NewAxisComponent)
-
-
-class NewTickLabelComponent(TickLabelComponent):
-    adapts(IAxis)
-
-    def render(self):
-        return " ".join([ "q%i" % i for i in range(self.axis.start, self.axis.end)])
-
-gsm.registerAdapter(NewTickLabelComponent)
-
+# # The following statements can be uncommented to illustrate how to swap classes.
+# #
+# # This example shows how to swap all Axis components which parents are a ViewBoxes to be of class NewAxisComponent
+# class NewAxisComponent(AxisComponent):
+#      adapts(IViewBox)
+#
+# gsm.registerAdapter(NewAxisComponent)
+#
+# # This example shows how to exchange the TickLabelComponent for all Axis
+# class NewTickLabelComponent(TickLabelComponent):
+#     adapts(IAxis)
+#
+#     def render(self):
+#         return " ".join([ "q%i" % i for i in range(self.axis.start, self.axis.end)])
+#
+# gsm.registerAdapter(NewTickLabelComponent)
 
 
 image_data = [1,2,3,4]