A boy's body starts changing when he is in between 11 and 20. Many boys worry that they are not developing fast enough. Remember, each person has his own timetable.
Some boys start puberty early, and some start later.
You will go through puberty at your own speed. Most of the changes of puberty are caused by the male hormone testosterone which the body is starting to produce. Testosterone is made in the testicles. The testicles are inside a sac or bag below the penis, called the scrotum. As the amount of testosterone increases, the scrotum gets darker.