Children of the same chronological age can differ by several years in their level of biological maturation. Growth, development and rate of maturation is the result of a complex interaction of genes, hormones, nutrients and the environments (physical and psychosocial) in which the individual lives.
This combination of factors regulates the child's physical growth, neuromuscular development, sexual maturation, mental, cognitive and emotional development, and general metamorphosis during the first two decades of life.
Puberty is characterized by numerous physical changes by which a child's body matures into an adult body capable of reproduction. These events occur over a number of years and include major changes to height, deposition of fat, bone and muscle, transformation of the brain, and acquisition of secondary sexual characteristics (e.g. breast, genitalia, pubic and auxiliary hair growth).