As children develop into adolescents, they go through physical, emotional and cognitive changes. Their physical changes occur first, making them appear adult-like, yet they are still emotionally immature. Aside from acne and an increase in body odor, the most prominent physical changes that occur to adolescents are the maturing of the genital organs, or puberty. Although the timing of puberty varies a great deal between adolescents, as a rule, girls develop earlier than boys.

The onset of menstruation marks the beginning of puberty for girls. Once a girl begins menstruating regularly, she is capable of reproduction. Other physical changes girls go through include an increase in body hair, the emergence of breast tissue and rapid growth. The average age for puberty in girls is 12.5 years old. Girls who mature earlier tend to feel awkward around their less developed friends and might feel inhibited from playing sports. In addition, they might be mistaken for an older woman and thrust into situations to which they aren't emotionally ready. On the other hand, girls who mature late worry whether their body is functioning normally.

As opposed to girls, boys enter puberty gradually, not as a result of a single event. The physical changes in boys -- between the ages of 13 and 17 -- include rapid growth, an increase in body and facial hair, developing sexual organs and undergoing voice changes. In addition, as boys develop sexually, they release nocturnal emissions. The average age for boys to enter puberty is 14 years old. Boys who mature earlier are looked upon as leaders as well as athletes, since they obtain increased muscle strength and speed at a younger age. On the other hand, boys who mature late are often teased; however, this usually stops when they catch up to their peers, as they inevitably do.