Over a million people have bought the new Apple iPad. However, using it right before bed could cause insomnia! So could your iPhone and the new computer tablets Nokia and Hewlett-Packard plan to have out for Christmas. If you use an Amazon Kindle or a Barnes & Noble Nook e-reader, you'll be fine. Why? According to the website Tech News Daily, it's because of a big difference in the technology. The Kindle and Nook are only for reading. They use black-and-white "e-paper" graphics that mimic the printed page. Since the screen doesn't emit light on its own, you need an outside light source - like a reading lamp. You can even use it in direct sunlight. On the other hand, the iPad uses a full-color liquid crystal display that has to be back-lit - like a TV or computer screen. This means, you can read an electronic book in a dark room. Or watch a video, answer email or surf the Internet without turning on a light. Since the iPad and the iPhone beam light directly into your eyes - they can also keep you from sleeping, if you use them too close to bedtime. That's because bright light - especially the frequency of blue light that these devices emit - mimics the daytime sky. That reduces your production of melatonin, the hormone that tells your body it's bedtime. Since most people hold an iPad or iPhone relatively close to their face, it reduces melatonin production even more than watching a TV from across the room. So, how can you make sure you get a better night's sleep? If you have an iPad, don't use it - or your iPhone, TV or computer - within an hour of going to sleep. Also, keep your bedroom dark. Even a small amount of brightness from a cracked curtain or digital display can enter your retina when your eyes are closed. That'll send a signal to your brain that it's time to be awake. So, remove any electronics from your bedroom that emit blue light - like computers, TVs, DVD players, and even your digital clock! * If you have to read before bed, grab a good old-fashioned book. That way, when you close your eyes, your body will be ready to sleep.