REM-сон, or Rapid Eye Movement sleep, is a unique phase of the sleep cycle characterized by quick movements of the eyes, increased brain activity, and vivid dreams. This stage typically occurs about 90 minutes after falling asleep and recurs several times throughout the night, making up about 20-25% of total sleep time. During REM-сон, the body experiences temporary muscle paralysis, preventing individuals from acting out their dreams. This phase is essential for cognitive functions such as memory consolidation, learning, and emotional regulation, highlighting its importance for overall mental health and well-being.