Sleep Stages

SWS (aka deep sleep or NREM3), REM, and Light-Sleep (aka NREM1 and NREM2) are all stages of sleep.

• SWS (Slow-Wave Sleep) is a vital sleep stage, and the deepest stage of sleep, during which the glymphatic system is activated.
• REM (Rapid-Eye Movement) is a vital sleep stage, and is most well-known for having more frequent occurrences of dreaming.
• Light-Sleep is a non-vital sleep stage (though it is theorized that it is healthy to have at least 20% light sleep in your core(s)). It is mostly a transitional stage of sleep, though it serves other purposes, and is usually the most pleasant to wake from.

The average sleep cycle is 90m long, though they can vary person to person. They usually begin with Light Sleep, then transition to SWS, Light Sleep, and then REM, before restarting.