Sleep: We all do it, and we must, but why? What advantage does spending a third or more of our hours immobile give us? The shortest answer is that sleep is necessary to clear out the buildup of adenosine in the brain. The longer answer is considerably more complex. If you have seven minutes to dig into the function of sleep on a neurological level—plus some historical tidbits on segmented sleep—this It's Okay To Be Smart video is your ticket:

If you're looking for a kid-friendly (and non-video) explanation, check out our recent article Why Do I Have to Go to Sleep? Also relevant: Why Do I Always Wake Up 5 Minutes Before My Alarm Goes Off? And 7 Reasons Sleep Makes You a Better Person.