Puberty

Puberty is the period during which adolescents reach sexual maturity and become capable of reproduction. In humans this usually starts around the early teens as boys and girls develop physical features (such as facial hair and breasts) that mark them as men and women.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Smurfs enter this period as they reach early adulthood at 100 years of age, although natural-born Smurfettes reach it much earlier as their breasts begin to develop. The onset of "the Smurfette dream" among male Smurfs is usually when he is physically capable of becoming a father. However, facial hair doesn't usually develop until the male Smurf is around 300 years of age.