One person's trash is another's treasure. But what of his waste?

The Smithsonian has unexpectedly shared five unexpected uses for urine -- including whitening your teeth and making own gunpowder.

"For modern scientists, the golden liquid can be, well, liquid gold," wrote the museum's Surprising Science columnist. "But a quick look back in history shows that urine has always been important to scientific and industrial advancement."

Here's a few historic uses for urine that will have you saying, gee whiz!