In the last century, our sleep patterns have been heavily influenced by artificial light sources. (Think about your smartphone.) In this instructive talk, sleep researcher Dragana Rogulja outlines the damage this does to our health and suggests some ways to combat the problem.
3Blue1Brown, by Grant Sanderson, is some combination of math and entertainment, depending on your disposition. The goal is for explanations to be driven by animations and for difficult problems to be made simple with changes in perspective.