The pineal gland, also called epiphysis, is a gland that secretes hormones that control the body's biological clock, since it regulates the sleep-wake cycle (circadian rhythms). It is located in the central part of the brain since ancient times and is recognized as a gland perceives the environment. When light decreases, the pineal gland is responsible for producing melatonin, a neurotransmitter that induces sleep. Furthermore, melatonin is also an antioxidant and powerful regulator stress as cells regenerated. Therefore, its production discouragement and low morale that produce the seasons of autumn and winter, against the revival of energy that cause relates sunny days.