Adolescence is the transitional stage between childhood and adulthood, generally covering the age group of 10 to 19 years. It is a period of rapid physical, emotional, cognitive, social, and psychological development. During this stage, young people experience several changes that gradually prepare them for adult roles and responsibilities. One important characteristic of adolescence is rapid physical growth. Adolescents experience changes in height, weight, body shape, and physical strength. Puberty brings changes such as development of reproductive organs, growth of body hair, voice changes in boys, and development of breasts and the beginning of menstruation in girls. For example, a 13-year-old boy may experience a sudden increase in height and deepening of his voice, while a girl of the same age may begin menstruating. Another characteristic is sexual maturation. Adolescence marks the development of secondary sexual characteristics and reproductive maturity. Hormonal changes influence physical appearance as well as emotional responses. Adolescents may become increasingly conscious of their physical appearance and may compare themselves with their peers. For example, a teenager may become concerned about acne, body weight, height, or hairstyle because