There are many things that the current science cannot explain; "Why Creatures were created", "How the world was created", or so on. In these things, the reason why creatures sleep is one of the most misterious things. All creatures incuding human do sleep every single day and, for examnple, human sleep for about 6 hours fer day and it takes 40 percent of time in his or her life. Concidered as scientifically, it is waste tme and has a danger that a predeter might atack while sleeping. There must be a benefit or reason of sleepining and there is no answer and no evedence to prove if it is true or not. As one(my) hypothesis, it is because sleeping is the turning point to go to another world. Only things people believe are science that has been proved only in this world and the things they can feel and since. They cannot see themselves sleeping in their own sight, even if they can see others sleeping. Nobody knows what happens after sleeping, so there is no evidence that the world is connected to the time before sleeping and after waking up. The brain is convinced if it is connected refer from the science which is made only in that world. For example, if something strange happened in the dream, the parson in the dream does not think it is natural and, after waking up, he or she finds the happening in the dream strange. In short, there are many worlds and sleeping is the turning point to go to another world. In addition, all dreams taken as dreams are not dreams but other real worlds.