如何让这个div从顶部滑下来，使用jQuery?

So I have 2 divs children of a display block parent. I would like to make div #2 (green) be on top of div #1 (red). With "on top" I'm not talking about z-index, I'm talking about literally being on top of the other. And then I was wondering if there could be a way to make div #2 slideDown()So I have 2 divs children of a display block pa