REM (Rapid Eye Movement) is a unique phase of sleep characterized by quick movements of the eyes, increased brain activity, and vivid dreams. It typically occurs about 90 minutes after falling asleep and recurs several times throughout the night, with each episode lasting longer as sleep progresses. During REM sleep, the body experiences temporary muscle paralysis, which prevents individuals from acting out their dreams. This stage is essential for cognitive functions such as memory consolidation, learning, and emotional regulation, making it a vital part of a healthy sleep cycle.