If we look into the dictionary, we find out that nudism is: “a movement of nudity promotion and its practicing”. The word has its origin in the Latin “nudo”, that means “naked”. But evermore there is in this connection a more modern term used, and that is “naturism”. It comes from the Latin word natura, which means “nature”. If with nudism we mean the promotion and practicing of nudity as such, naturism is more concentrating on the return of the man to the nature through his dwelling without clothes in a natural environment of the nature. Why do we wear underwears? This is an interesting a worthwhile question. In the medical view point, apart from making us feel secure mentally, underwears serve no other functions. Somebody even feel that underwears are the source of pressure. Somebody have done an experience with monkey, making them wear shorts, the monkey being bound died a week later. There are many kinds of pressure in today’s society; you may put away all other things, using the method of “Naked Sleep” to have a good sleep. Human being originally has the ability to produce enough heat. Also, when our skin touches some cloth, our body will feel warm gradually, and we may eventually fall asleep.