One of the earliest changes of puberty is that you suddenly grow taller very fast. This is caused by substances called hormones, which are produced by special glands in your body. The puberty beginning varies from person to person and betwen the sexes. The average age is usually 11 for girls and 13 for boys. So, for a while, girls tend to be taller than boys. However, this is not true for everybody, because some girls can reach puberty any
time between the ages of 8 and 17 and boys between 10 and 18! Two people of the same age can be very different – one is very tall, the other is very short; one has a deep voice, the other has a high voice, etc. This sometimes causes embarrassment. But it is completely normal. The sudden grownth, like every other change of puberty, varies with the individual. Your final height is determined mainly by what you have inherited from your parents.