This chapter describes the beginning of puberty, the timing of puberty and off-time puberty. Puberty is marked by striking differences between the physical development of males and females. The puberty process is an illustration of the magnificent way in which multiple systems in the body interact to produce growth. Puberty is initiated in the hypothalamus, an almond-sized structure in an area of the limbic system called the midbrain. As a child nears the adolescent years, and a threshold level of body fat is reached, fat cells produce the hormone leptin, which provides the signal to the hypothalamus to begin the puberty process. Parents, teachers, or mental health personnel should prompt discussions about the emotions linked with having the first period, feelings connected with the rite of passage of menarche, and the mixed feelings associated with puberty, such as the combination of embarrassment and pride.