I have a application with one Grid that is displayed when the application starts. With a additional button I add 2 other Grids. This works with a ViewStack around the 2 optional Grids. The 3 Grids are horizontal. Now when I minimize the application I want the Grids change to vertical. I found the flexlib library with the "FlowBox" class. My question is now: How can I add the 2 Grids inside the ViewStack to the FlowBox so they change to vertical one by one, depending on how much I minimize the window.