While making complex Flex UI, it is very easy to get lost within the COmponent hierarchy, expecially when the hierarchu is very complex and design view is not practical to use.
In this case, here is something which I have found to be extremely helpful:
In your css file, ass borders for the generic components, like this:
| Application { } VBox { Panel { |
This will add a black border to all components and help you demarcate the boundaries of all the components in use. When you are done, just take them off.
