Sliding Down A Small NSView Over An Existing NSView

I'm working with a NSWindow that displays various NSViews when buttons are pressed 开发者_StackOverflow中文版(a settings panel, essentially). I'm trying to get a smaller NSView to slide out with a NSPopUpButton and some NSButtons from the top of the main NSView when a button is pressed.

What's a good starting point for figuring out how to do this?