Sleep Cycles and the Stages of Sleep, Defined

There are four stages of sleep that make up a sleep cycle. Over the course of a night, your brain will transition through the various stages of sleep multiple times.

REM, Light, Deep: How Much of Each Stage of Sleep Are You Getting? - Fitbit Blog

What Is REM Sleep? Definition and Benefits

5 Stages of Sleep: Psychology, Cycle & Sequence

Sleep: Stages And Sleep Cycle, Functions

Stages of Sleep: What Happens in a Sleep Cycle

Sleep Stages and Sleep Cycles Explained

Example of variation of heart rate (15-min mean) due to sleep stage

The 4 Stages Of Sleep — Cycles, Phases, and Improvement

Stages of Sleep Introduction to Psychology

Sleep Stages & Sleep Cycles