A 90-minute sleep cycle refers to the natural progression of sleep stages that typically occurs in approximately 90 minutes. Each cycle includes various stages, such as light sleep, deep sleep, and REM sleep (Rapid Eye Movement). These stages help the body recover and rejuvenate, playing a crucial role in overall health and well-being. During a typical night, a person may experience multiple 90-minute cycles, usually totaling around 4 to 6 cycles. Understanding this cycle can help individuals optimize their sleep patterns, ensuring they wake up feeling refreshed and alert by aligning their wake time with the end of a sleep cycle.