Pop quiz! What does your pineal gland do? Most people know it as a little blob in your brain that makes melatonin. Melatonin is a hormone that's made when it gets dark outside. Your eye has really cool photoreceptor cells that sense light, so it can tell the brain (and pineal gland) that it's time to start making melatonin. Melatonin makes you sleepy and lowers your body's temperature. Have you ever taken a trip to a different time zone? Even a change of one hour can be annoying, right? It's because your body already has an established "sleep/wake cycle." That means you will still get sleepy at the same time, but the daylight (or darkness) outside will not agree with you! Your body is used to making melatonin at similar times every day, so even if you fly halfway across the globe (a 12 hour difference), you will have jetlag: aka a hard time staying awake during a bright, sunny day! There's more. Melatonin is also a powerful antioxidant. Antioxidants keep cells from being damaged by free radicals. Read more about antioxidants and free radicals here!