Why We Sleep

The science behind sleep — what it’s for and why we need it.What is sleep? Why do humans need to spend a third of their lives immobile, passed out, and experiencing strange visions? In this Snapshot, you’ll learn about the cutting-edge research that demonstrates links between sleep disruption and health problems, including dementia. You’ll also learn whether animals sleep like people, what dreams are for, and if sleeping pills are good for you.