Why do we need belly buttons?

We all have a belly button. Right there, in the middle of our belly, there’s a nub. Some go in, some stick out, but what exactly are they for? We asked pediatrician Emma Gerstenzang to help us find the answer. Got a question that’s hard to stomach? Send it to us at BrainsOn.org/contact, and we’ll help digest the answer for you! See omnystudio.com/listener for privacy information.