Sleep

"Scientists used to think that people were physically and mentally inactive during sleep."

https://www.webmd.com/sleep-disorders/ss/slideshow-sleep-body-effects?ecd=wnl_gdh_020126&ctr=wnl-gdh-020126_supportBottom_title_2&mb=Bw69jj4V%403Xd0vWN4nAvZhsBxqZqfebCTdGTM0BbxsM%3d