Your phone, tablet, and other screens can mess with your sleep. The reason? They give off blue light, which signals your body to stop making melatonin, the hormone that controls when you feel sleepy. Instead, this light tells your brain to stay alert. Not to mention the late-night dings and buzzes that can jolt you out of peaceful slumber. The best bet for better sleep is to keep computers, TVs, and, yes, your phone out of your bedroom.