Hippos navigate by it, sloths keep in touch through it, dung beetles eat it... and most grownups would rather not to mention it. Meanwhile, scientists who study animal feces find out all sorts of things, such as how many insects a bat eats or just what technique a T. rex used to devour a triceratops 70 million years ago. However you look at it, poop is the quintessential prototype for recycling and probably the most useful stuff on earth. Take a peek at Poop and find out all you need to know-what it's for, where it goes, and how much we can learn from it.