What makes us sleepy? What happens when you don't sleep? How do you sleep better? Avoid sleep anxiety and listen to Teagan and Bekah explain the intricacies of sleep.
https://www.sleepfoundation.org/ an evidence based website I recommend for the layperson.
https://www.youtube.com/watch?v=3mufsteNrTI
https://healthysleep.med.harvard.edu/healthy/matters/benefits-of-sleep/why-do-we-sleep
https://www.livescience.com/19462-fall-asleep.html
https://www.sleepfoundation.org/how-sleep-works/stages-of-sleep
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2814941/
https://www.verywellhealth.com/symptoms-of-sleep-paralysis-3014781
https://www.healthline.com/health/sleep-deprivation/sleep-deprivation-stages#lifestyle-tips\
https://rarediseases.org/rare-diseases/fatal-familial-insomnia/
https://www.sleepfoundation.org/narcolepsy
https://my.clevelandclinic.org/health/diseases/14292-sleepwalking
https://kidshealth.org/en/teens/sleep-start.html
https://www.sciencealert.com/humans-used-to-sleep-in-two-shifts-maybe-we-should-again