Your brain has an internal clock, called the SCN (suprachiasmatic nucleus). When the brain gets signaled that it is nighttime, the SCN sends messages to the pineal gland. The pineal gland controls melatonin, which is a chemical that gets you tired/sleepy. When you sleep, you store new information that you learned that day, and you get rid of toxic waste. The main benefit for your nerve cells is to keep your brain healthy while storing the new information. The nerve cells reorganize and repair the new data. Another sleeping benefit is conserving energy. It helps lower the need for calories because while sleeping, your metabolism is slowed. The restorative theory suggests that in order to restore yourself, you need sleep. Skin renewal is the most common restoration.

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https://www.hopkinsmedicine.org/health/conditions-and-diseases/sleepwake-cycles

https://www.healthline.com/health/why-do-we-sleep#:~:text=Many%20biological%20processes%20happen%20during,molecules%20like%20hormones%20and%20proteins.