Tanner Staging

	Genitalia
Stage I (Prepubertal)	Size and proportions of the testes, scrotum, and penis are approximately the same as in early childhood.
Stage II	Enlargement of the scrotum and testes, changes in the texture of the scrotal skin. The scrotal skin may appear somewhat reddened, but differences cannot be distinguished in black and white images.
Stage III	Further development of the scrotum and testes, with the penis beginning to grow, mainly in length, but some increase in penile circumference as well.
Stage IV	Further enlargement of the scrotum and testes, further darkening of the scrotal skin, but photos are difficult to identify. The length and circumference of the penis increase further, with development of the glans.
Stage V	Size and shape of the genitalia are the same as in adults. After reaching stage V, the genitalia do not increase further in size.

Puberty is the period during which secondary sexual characteristics begin to develop and reproductive capability is acquired.