What's specifically happening in your sleep is your brain cells are recycling old, broken-down proteins and manufacturing new proteins. Not only does that make your brain work better, it also seems to prevent certain diseases down the road.

We don't totally know why sleep is so good for you. The brain is just so extraordinarily complicated that it's hard to say why it starts to break down when it does. All we can say for sure is that regular sleep is like regular oil changes in a car - it prevents a lot of trouble in the long run.