Sleep is one of those funny things about being a human being -- you just have to do it. Have you ever wondered why? And what about the crazy dreams, like the one where a bad person is chasing you and you can't run or yell. Does that make any sense?

If you have ever wondered about why people have to sleep or what causes dreams, then read on. In this edition of HowStuffWorks, you'll find out all about sleep and what it does for you.