Sleep cycles through four distinct stages—N1, N2, N3, and REM—each serving unique functions from memory consolidation to emotional processing and brain waste clearance. Dr. Gina Poe reveals how consistent bedtimes align with circadian clocks to trigger growth hormone release, why alcohol destroys sleep quality, and how REM sleep's neurochemical silence enables trauma recovery by divorcing emotions from memories during consolidation. The first 90-minute sleep cycle releases a major bolus of growth hormone and initiates brain waste clearance through slow-wave sleep; missing this phase by sleeping later means missing these benefits entirely, not delaying them.