+A sleep cycle is the brain's nightly journey through distinct [Sleep Stages](/wiki/sleep_stages). Each cycle, typically 90 minutes, shifts between [NREM](/wiki/nrem)'s restorative depths and REM's vivid dreams, repeating several times.
+## See also
+- [Sleep](/wiki/sleep)
+- [Dreams](/wiki/dreams)
+- [Circadian Rhythm](/wiki/circadian_rhythm)
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