Add a VBox to overlap
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Canvas width="100" height="100" backgroundColor="#999999"> <mx:VBox id="b1" width="80" height="80" x="20" y="20" backgroundColor="#00FF00"> </mx:VBox> <mx:VBox id="b2" width="50" height="50" x="0" y="50" backgroundColor="#FF0000"> </mx:VBox> </mx:Canvas> </mx:Application>