Puberty is the period when the child experiences physical, hormonal, and sexual changes and becomes capable of reproduction. It is associated with rapid growth and the appearance of secondary sexual characteristics.
Adolescence is the period of transition between puberty and adulthood.
The hypothalamus and pituitary glands, hormone secreting structures in the brain, produce hormones that, among their other functions, control growth and maturation. When a healthy child is somewhere between 9 and 16 years old, he or she will enter puberty. The exact age depends on factors such as heredity and nutrition and whether the child is a boy or girl. On and average, boys enter puberty 2 years later than girls. In boys, the testicles increase production of testosterone.