Watch these recommended TED-Ed Lessons:What would happen if you didn’t sleep?In the United States, it’s estimated that 30 percent of adults and 66 percent of adolescents are regularly sleep-deprived. This isn’t just a minor inconvenience: staying awake can cause serious bodily harm. Claudia Aguirre shows what happens to your body and brain when you skip sleep.The benefits of a good night’s sleepIt’s 4am, and the big test is in 8 hours. You’ve been studying for days, but you still don’t feel ready. Should you drink another cup of coffee and spend the next few hours cramming? Or should you go to sleep? Shai Marcu defends the latter option, showing how sleep restructures your brain in a way that’s crucial for how our memory works.What causes insomnia?What keeps you up at night? Pondering deep questions? Excitement about a big trip? Stress about unfinished work? What if the very thing keeping you awake was stress about losing sleep? This seemingly unsolvable loop is at the heart of insomnia, the world’s most common sleep disorder. So what is insomnia? And is there any way to break the cycle? Dan Kwartler details the science of insomnia.How does your body know what time it is?Being able to sense time helps us do everything from waking and sleeping to knowing precisely when to catch a ball that’s hurtling towards us. And we owe all these abilities to an interconnected system of timekeepers in our brains. But how do they work? Marco A. Sotomayor details how human bodies naturally tell time.Why do we dream?In the 3rd millennium BCE, Mesopotamian kings recorded and interpreted their dreams on wax tablets. In the years since, we haven't paused in our quest to understand why we dream. And while we still don’t have any definitive answers, we have some theories. Amy Adkins reveals the top seven reasons why we might dream.