We already know that bats are amazing creatures. They are the only mammals that can fly. The bones in their wings resemble our fingers. They account for about one in five of all mammals living on the planet. And some can fly up to 99 miles per hour! But have you ever asked yourself why the heck they sleep upside down? We asked biologist DeeAnn Reeder to help us find the answer. Got a Moment of Um question that’s turning you upside down? Send it to us at BrainsOn.org/contact, and we’ll help get it all sorted out.