Do you know that your sleep basically can be devided to two parts. The REM sleep and the slow wave sleep. Actually the REM sleep is a very interesting phenomina. Eventhough you are sleeping in REM sleep your brain activities are increased to the normal level. During the REM sleep you see all the dreams. And the other interesting thing is people get rapid eye movements during the REM sleep> So the scientists blieve that it perform some important functions that are still unknown.