General changes during puberty:
The testicles get larger and the scrotum starts to hang lower: 10-13,5 years (average: 11,8 years).
Thinning and reddening of scrotum: 12 years
Start of pubic hair growth: 10-15 years.
Becoming taller: 12-16 years (average growth peak: 14 years, normally 1 year after increase of testicle size).
Increase of penis size (first in girth, then in length): 11-14,5 years (normally 1 year after the testicles have increased in size, with most guys the penis will not become much longer after they turned 16).
Voice breaking: 11-14,5 (average:13,5 years).
First ejaculation: 11-15 (on average between 13 and 13,5, normally 1 year after the penis has increased in size).
Axillary hair, body hair and facial hair: 2 years after the growth of pubic hair.
Full beard growth: 4-5 years after the growth of pubic hair. Beards grow slowly at first, the hairs being sparse and light.