Girls start in age of 12 - 13 but boys start in age of 14-15. So girls puberty start first.

Puberty is the period of physical and sexual maturation that occurs during adolescence. It is a time when the body undergoes various changes, including the development of secondary sexual characteristics. While the timing of puberty can vary among individuals, there is a general pattern that can be observed.

Puberty in Girls:
Puberty in girls typically starts between the ages of 8 and 13, although it can begin as early as 7 or as late as 15. The first sign of puberty in girls is usually the development of breast buds, which is followed by the growth of pubic hair and the onset of menstruation (menarche). Menarche usually occurs around the age of 12, but it can happen as early as 9 or as late as 16. Along with these physical changes, girls also experience growth spurts and changes in body shape.

Puberty in Boys:
Puberty in boys usually begins later than in girls, typically between the ages of 9 and 14. The first signs of puberty in boys include testicular enlargement and the growth of pubic hair. This is followed by the growth of facial and body hair, deepening of the voice, and an increase in muscle mass. Boys also experience growth spurts during puberty, and their bodies undergo changes in shape and size.

Why Girls Experience Puberty Earlier:
There are several reasons why girls tend to start puberty earlier than boys:

1. Hormonal Differences: The onset of puberty is triggered by hormonal changes in the body. Girls have higher levels of estrogen, which is responsible for the development of secondary sexual characteristics. Boys, on the other hand, have higher levels of testosterone, which leads to the development of male secondary sexual characteristics.

2. Genetic Factors: The timing of puberty is influenced by genetic factors. Research has shown that there is a genetic component to the age at which puberty begins. If a girl's mother started puberty early, there is a higher chance that the daughter will also start puberty early.

3. Environmental Factors: Environmental factors such as nutrition, health, and stress can also influence the timing of puberty. Girls who have a healthier lifestyle and better nutrition may start puberty earlier.

Conclusion:
In conclusion, girls generally start puberty earlier than boys. This is due to hormonal differences, genetic factors, and environmental influences. However, it is important to remember that the timing of puberty can vary among individuals, and there is a wide range of normal development. If there are concerns about the timing or progression of puberty, it is best to consult a healthcare professional for guidance and support.