Sleeping means body will stop its activity, most feeling closed, muscle weakness, unsocial reclusive, the reduction of metabolism, it can ensure body's basic vital activity under the least energy consumption. It is a reversal state, it can immediately complete transition between sleeping and wake, it is very different for the state of hocus and sleeping.
Scientific information shows sleeping is not only the stop of active, but also it can keep the best state. Sleeping plays a vital role in studying and searching spirit.

Human need 1/3 time of their life to sleep. The reason that people must sleep is that cerebra need to relax and maintain some most important neuron group in deep sleep. There are 10 billions nerve cells in human cerebra which transfer messages to all the body corners, unused nerve cell will atrophy and even die.  Also, some study & testing show that a person whose sleep less 4 hours will catch a disease more easier than those whose sleep time reach 7-8 hours.