Mad Science

There is a fun trick that amuses children to no end in which you put about a teaspoonful of water in an otherwise empty pop can, and heat it on the stove until you see vapor wafting out the hole in the top. Next to the can, you pre-position a cookie tray with about 1/8 in of cool water in it. When the can is steaming, you take it with a pair of tongs, and quickly invert it onto the cool water. The can will collapse, pretty completely, and quite rapidly.
On a somewhat larger scale, here's a video of somewhat the same trick being done.

Link

H/T: Big Stupid Tommy