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normally lasts up to ten minutes and is a state from which you can be easily wakened. Stage 2 sleep is a very light sleep. Your eyes are closed; your heart and breathing rates slow even more; your muscles relax. But you can still be wakened easily. Stages 3 and 4 are the deepest type of sleep and the most difficult to wake from. These stages provide the kind of rest that best restores our bodies and minds. Most people reach stage 3 about 20 minutes after lying down. They usually reach stage 4, the deepest type of sleep, within about an hour. The Sleep Cycle: REM If you watch someone sleeping, you can tell if they have entered REM sleep by watching their eyes. Their eyes dart from

Experts believe that REM sleep is an important part of brain development.