Human skin is a cornucopia of fragrances.
The bacteria living on our skin emit more than 200 odor chemicals.
"Many of these molecules smell quite pleasant," says biologist Jeff Riffell at the University of Washington. "They smell grassy or a little bit like mushrooms. Some human scents are the same ones found in flowers."
Other chemicals — well — they aren't so nice. "They're pretty funky," Riffell says, like an overripe Brie cheese or a musty basement.