When yоu gо tо sleep аt night, you probаbly think thаt you are not doing much. Your body is in one place, your eyes are closed, and you don’t talk to people. But your body is doing more than you think it is! Scientists have used special, sophisticated machines to study the way people sleep. They have found that your brain is actually very busy when you sleep. There are several stages of sleep in a sleep cycle. You go through the sleep cycle multipletimes each night. Your brain’s activity level is a little different in each stage. The final stage of the cycle is called rapid eye movement (REM) sleep. During REM, your eyes are moving even though you are asleep. That is how this stage got its name. Most of your dreams occur during REM sleep. What is your brain doing while you are sleeping?