 Puberty which starts earlier than usual is known as precocious puberty, and puberty which starts later than usual is known as delayed puberty.Notable among the morphologic changes in size, shape, composition, and functioning of the pubertal body, is the development of secondary sex characteristics, the "filling in" of the child's body; from girl to woman, from boy to man.Biologically, an adult is a human or other organism that has reached sexual maturity.