What happens to the human body when asleep?

Level: Intermediate

Some great sites for info about the body and how it works are the BBC and Kidshealth.

The BBC Science & Nature page is a good place to start.  Kidshealth site is also good.

We like the BBC site because it is good information from a reliable source. We like Kidshealth because it has good, reliable information and it's written for kids without all the scientific language.