Recreating "growth" effect

Hi people, wondering if you could help me out on a small issue here.

There is a specific effect I want to recreate with my own vector graphics, but I can’t quite figure out how to do it. One example of the effect can be found at:

The effect is the sliding ‘growth’ of the leaves as you mouse over certain sections, such as “build your own wetsuit”.

This isn’t the only example, I’ve seen it on several sites, but I’ve never been able to figure out how it can be done. I assumed previously it was some sort of masking effect, but it isn’t really working for me; How can it be recreated, and what actionscript makes it tick? (I’m fairly proficient with AS, but I can’t seem to find a good way to control it without individually scripting each piece to scale up in size, and tying it up with some messy timer intervals to get it to go in the right order; even then, getting it to run itself backwards is a complete pain, and it doesn’t look nearly as smooth as the example!)

Are there any tutorials on the subject? (I’ve had a good look but I can’t find anything).

Thanks in advance :slight_smile: