Adolescence is the period of transition between childhood and adulthood. It is the period of time generally between the ages of 12 and 17 years old and which begins in France around the age of 10 for girls and around 12 for boys. Adolescence is accompanied by numerous physical as well as psychological changes. The main transformation during adolescence is the appearance of secondary sexual characteristics: the growth of hair from the sexual organs, legs, and underarms, the changing of voice, the acceleration of growth, and the development of fat and muscle mass. This period is also accompanied by a psychological evolution which can, in some cases, be difficult for the soon-to-be adult.