“Why do we sleep?” is a very popular question that many humans ask today. Sleep is very sufficient for the human body. If it were not important, God would not have foreseen that a third of our lives would be occupied by sleep. During this time, many people are interested in knowing what is a good amount of sleep and what are the harmful effects of not getting enough sleep. The question “why do we sleep?” is a very difficult question to answer. One way to understand why sleep is important is to think of it as if it were food. Food helps us feel better and also helps the human body function properly. There are many different hypotheses about why we sleep. The first is that sleep allows the body to repair cells damaged by metabolic byproducts called free radicals. The production of these highly reactive substances increases during the day, when the metabolism is faster. However, scientists have found that the expression of genes involved in cell fixation increases during sleep. This hypothesis is consistent with the fact that smaller animals, which tend to have a higher level, are compliant...