When you don’t get enough sleep, you can feel drained, sluggish and lazy. So, we sip our coffee, attempting to make it through the day, until it’s time to slip back into bed. But besides the fact that we feel terrible if we don’t get enough, researchers have struggled to figure out why humans and animals sleep.

A new study by scientists at Bar-Ilan University in Israel, though, may help us find out. While studying brain activity in live zebrafish, they found that DNA repaired itself much