Beginning of puberty: 9.5 to 14 years old
First pubertal change: enlargement of the testicles
Penis enlargement: begins approximately one year after the testicles begin enlarging
Appearance of pubic hair: 13.5 years old
Nocturnal emissions (or "wet dreams"): 14 years old
Hair under the arms and on the face, voice change, and acne: 15 years old
Girls also experience puberty as a sequence of events, but their pubertal changes usually begin before boys of the same age. Each girl is different and may progress through these changes differently. The following are average ages when puberty changes may occur:
Beginning of puberty: 8 to 13 years
First pubertal change: breast development
Pubic hair development: shortly after breast development
Hair under the arms: 12 years old
Menstrual periods: 10 to 16.5 years old