?90-Minute CyclesYour brain cycles through light sleep, deep sleep, and REM roughly every 90 minutes all night.
?Sleep InertiaWaking mid-cycle triggers grogginess that lasts hours. End-of-cycle wakeups feel natural and alert.
⏱️14 Min to Fall AsleepThe average healthy adult takes ~14 minutes to transition from lying down to actual sleep onset.
⭐5–6 Cycles = OptimalAdults need 7.5–9 hours (5–6 full cycles) for complete cognitive and physical restoration.