Adolescence is the last major developmental stage from childhood to adulthood. It ranges from age 11 to 21. It is generally a time of self-discovery in which young people aim to define their place in the world.

The first part of adolescence encompasses the physical changes associated with puberty, or sexual maturation. Children’s bodies begin to produce more hormones and physical changes occur. In both boys and girls, more hair grows on the body, including pubic hair, and for boys, hair on the face. For boys, hormonal changes also mean growth of the sexual organs, greater frequency of erections and the ability to ejaculate semen from the penis. For girls, breast tissue grows, the hips widen and the monthly blood loss of menstruation begins. After menstruation begins (menarche), a young woman is physically capable of becoming pregnant.

The hormonal changes in both sexes are accompanied by greater sexual interest in other people. Teenagers may begin sexual behavior during this time, which may expose them to the potential for unwanted pregnancies and sexually transmitted diseases. The physical maturity may not be matched by a similar emotional maturity to handle such changes.

Many psychosocial changes are associated with adolescence. Teenagers may feel like they are adults but are not being treated as adults by their parents. Mood swings and emotional outbursts are common. They frequently test parental boundaries with risk-taking behaviors or general insolence. Some teenage rebellion is a normal part of growth. However, behaviors with serious consequences such as use of recreational drugs or alcohol and sexual recklessness can be a cause for concern. The emotional changes may be more serious for some teens, with thoughts of suicide or the potential for depression. Social changes in adolescence include greater activity and influences of peer groups.

In later adolescence, most overt physical changes have been completed. Girls typically finish growing by about age 16 and boys by about age 18. Physical changes that occur after this time may be the same as in any adult, related to nutrition and exercise. Good foundations about a healthy diet and regular exercise help teens at this stage to maintain healthy bodies.