One of the minor improvements in Flex 3 regarding layout is baseline alignment. Setting the baseline constraint means that the user is specifying an offset from the top edge of a constraint region or parent border and the control’s baseline. By offering a baseline constraint style, we can now allow multiple components to be constrained along a single shared baseline. Here is an example of two panels. One has no baseline set on the components. The other uses a baseline and a ConstraintRow.

The Panel using a baseline constraints looks like this:

Demo: simpleBaseline.swf

Source: simpleBaseline.mxml

At this time, you cannot set the verticalAlign style to a baseline. This is still an open bug: SDK-11725