25/02/2026
Why do people sleep?
Modern medicine’s understanding of sleep is like a partially assembled jigsaw puzzle. Experts can identify some of the pieces and have an idea of what the big picture looks like, but they haven’t figured out how everything fits together.
Your body cycles between being awake and asleep throughout each day, with certain processes only happening when you’re asleep. When you’re asleep, your body “powers down” and most body systems — including your brain — become less active.
Some of the key things that happen while you’re asleep include:
Energy conservation and storage. During the day, cells throughout your body use stockpiled resources to keep doing their jobs. While you’re asleep, your body uses less energy. That lets those cells resupply and stock up for the next day.
Self-repair and recovery. Being less active makes it easier for your body to heal injuries and repair issues that happened while you were awake. That’s also why being sick makes you feel more tired and need more rest.
Brain maintenance. While you’re asleep, your brain reorganizes and catalogs memories and learned information. This is like a librarian sorting and shelving books at the end of the day. It makes accessing and using things you learn and remember easier and more efficient.