Puberty is the process of sexual maturation and transformation that makes an individual capable of reproductive activity. It is characterized by physical changes such as the development of secondary sex characteristics, such as breasts in girls and facial hair in boys, and by psychological changes such as increased interest in sex and the ability to think about future events.
Puberty begins when the body starts producing larger amounts of the hormones testosterone in boys and estrogen in girls. These hormones cause physical changes such as the growth of pubic hair, underarm hair, and facial hair; the enlargement of the testes and ovaries; and the deepening of the voice. They also cause psychological changes such as increased interest in sex, more frequent thinking about sex, and greater awareness of one’s own body. The age at which puberty begins varies from individual to individual but is usually between 10 and 14 years for boys and 9 and 13 years for girls.
The physical changes of puberty generally occur over a period of 2 to 5 years. In girls, breast development typically begins around age 10 or 11, while menstruation (menarche) usually occurs around age 12 or 13. In boys, testicular enlargement typically begins around age 11 or 12, while penis growth usually occurs around age 13 or 14. The first ejaculation usually occurs around age 14 or 15.
After puberty has begun, individuals continue to grow until they reach their full adult height (usually around ages 16-18 for boys and 14-16 for girls). Once an individual has reached his or her full adult height, he or she stops growing taller but may continue to develop muscle mass into his or her early twenties.