REM Sleep or Rapid Eye Movement Sleep is a very important stage for human health. REM sleep is the stage when your brain is active, dreams occur, and your eyes move back and forth rapidly under your eyelids. During this stage, your brain is very active! The brain organizes information it learned the past day in a long-term memory storage. This is the most puzzling sleep stage for scientists! You go through 3 REM sleep stages in a night. REM sleep is the stage when your body goes into a recovery mode. This is also the stage where you grow taller and stronger. REM sleep also helps you fight off infections like viruses or bacteria. The cells in your body are very active during this stage and are ready to attack any virus or bacteria. This stage is one of the very important stages in sleep.