The trick is simple. Wrap the content with a zero height div, hide it with absolute positioning, change the height, and wait the browser to use CSS3 transition to finish the trick.
Requirements: AngularJS 1.0.0+
Live demo: here
list 'angular-collapse' as a dependency for you app.
include the supplied CSS file (or merge them within your own).
add 'collapse' directive to your content. For example,
Why I created this
This is really a simple and basic requirement, that has a solution already in Bootstrap. But I found no one available around for Angular, or maybe it's too small to be a standalone module.