Sleep is much more important than anybody ever imagined and sufficient sleep is the cure to a large percentage of western societies problems. There are few financial incentives in promoting sleep so we do not hear about this over drugs, caffeine etc.
REM sleep is the source of creativity and thought resolution where different parts of the brain communicate that do not usually. Rem sleep occurs in the last two hours of an 8 hour sleep.
Non rem sleep is where the brain clears itself of the byproducts of brain activity. Without this the brain becomes damaged and is probably the cause of dementia.
Sleeping pills, LCDs, artificial light, caffeine, alarm clocks, early school starts and alcohol are all very bad.
Sleep in a dark room at 18 degrees celsius for 8 hours, allowing 1 hour to fall asleep.
Slight quibble: the fraction of REM sleep in each sleep cycle is highest during the last sleep cycle of the night.
He’s the director of UC Berkeley’s Center for Human Sleep Science, so you could also look up his lab’s scholarly publications https://www.humansleepscience.com/p-u-b-l-i-c-a-t-i-o-n-s