In recent years, a lot of people are struggling with getting sleep until late night. There are various reasons why they have difficulity in having sleep, but the main reason for this problem is closely associated with using cellphone before they go to bed. Nowadays, there are many functions for using mobile phone. For example, one of the most poplular functions, internet provide people to watch movie, to enjoy short video clips on Youtube channels and play the mini games. Therefore a lot of users enjoy the entertaning contents mentioned above, this makes them to interrupt their good sleep because phones have negative effects on human's body rythmn. Some people argue that using cellphones brings the excitedment and joy. However, I think that some drawbacks of spending the time with phones outweigh the their benefits. As I mentioned above, while using phone before students go to bed, the harmful energy from the phone changes their body rythmn and sleep's pattern. In addition, unstable...