During adolescence (usually encompassing ages 10 to the late teens or early 20s), children become young adults. They mature socially and physically. Notably, they become sexually mature and socially independent. During this time, the adolescent develops a sense of who he or she is and learns to form intimate relationships with people who are not members of the family. Guiding adolescents through this intricate period of development can be a challenge for parents. Risk-taking (such as engaging in violence and binge drinking) is common among adolescents and causes acute health risks. Unhealthy behaviors such as smoking or drug use, which cause serious problems later in life, also typically begin in adolescence.
Resource: Merck Manual Home Edition