Infancy is the fastest growing period in a person’s life, with weight reaching more than three times the birth weight at the age of one and length growing by an average of 25cm a year. Girls enter puberty on average two years earlier than boys, boys enter puberty at about 12-13 years old, which is more common for boys, but there are also boys who enter puberty at 10-11 years old, and most girls enter puberty at 9-10 years old. The fastest growing year of puberty for girls can reach a height of 8-10cm, and the fastest growing year for boys can reach 10-12cm.