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.thensf.org/

https://www.youtube.com/watch?v=3mufsteNrTI

https://lionhabitatranch.org/about/lion-facts/#:~:text=They%20spend%20between%2016%20and,night%20when%20it%20is%20cooler.

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

https://www.pnas.org/content/117/40/25128

https://www.theguardian.com/lifeandstyle/2018/apr/17/sleep-billion-dollar-business-tiredness-spooning-robots-cuddle-blankets-luxury