The top layer is a ContainerControl of type ViewController
3. You design your interface on a ViewController.
Each ViewController is embedded in another ContainerControl of type StackController
2. The StackController is responsible for showing and hiding the embedded ViewControllers and provide a heading as well.
Finally StackControllers are embedded in a ContainerControl of type ScrollController
1 . These deal with scrolling if the shown embedded controls take up more space when is available.