Simple div animation on rollover

Simple div animation on rollover

Hello all,

I am trying to do something relatively simple, however, I don't have much jquery experience, so simple is not so easy for me :) All I am looking to do is make one div expand its height when another is rolled over.

<div class="button"></div>
<div class="changingBox"></div>

So basically, all I want is:
When the viewer rolls over the "button" div, the "changingBox" div will animate it's height. Lets go ahead and say the height is originally 20px and I want it to animate to 50px on the rollover. Also, I am curious if we can make the "changingBox" div go back to the original height on roll out. Thanks for your help in advance!