I'm pretty sure you haven't thought about this one in a while, or maybe ever. But researchers at North Carolina State University are: what lurks in the human belly button?

You wouldn't think that such a small area of the human body would yield much, but boy did it.  According to the research:

The team found over two-thousand species of bacteria, with nearly one-thousand-five-hundred of those species being new to science.

What did you think they'd find? Just a bunch of lint?

So what's the point of studying belly buttons? Part of the reason was to investigate claims that the organisms on human skin form the first line of defense against pathogens. The next step for scientists will be trying to figure out why certain bacteria live in certain people's belly buttons.

Here's what I want to know: does an 'outie' carry around as much bacteria as an 'innie'?  They didn't seem to cover that one!