non-REM sleep
All of sleep except REM sleep, from the lightest stages down to deep sleep.
Where it comes up
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01
What happens while we sleep?
What happens while you sleep: light, deep and REM sleep, how the cycles repeat through the night, and why brief wakings are a normal part of it.
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02
What is deep sleep, and am I getting enough?
What deep sleep is, why it comes early in the night and thins with age, and why a tracker's deep sleep number is only a rough guess.
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03
Why do we dream?
Why we dream, why dreams are so strange and borrow from yesterday, and what the main scientific theories say dreams are for.