"Why do we sleep?" has been a notoriously difficult question for scientists to answer, but, "What happens if we don't?" is actually pretty simple — nothing good. Not getting enough sleep can make you hallucinate, mess with your thinking and memory, and even lead to organ failure. And it doesn't take very long at all for these negative effects to start occuring. Here's what would happen to your brain and body, day by day, if you stopped sleeping.