The pattern of growth and development in children is mainly the development of height, weight and sex organs. Before the child reaches 3 years of age, there is a rapid increase in height and weight; between 3 years of age and puberty, the growth tends to stabilize; after puberty, there is a sudden increase in height and the development of the sex organs. From birth to 1 year of age, the average annual growth rate of children is about 20-25cm, and in some cases it can be as high as 30cm. From the age of 1 to 2 years, the average annual growth rate is about 10-15 cm; from the age of 2 years to puberty, the average annual growth rate is about 7-8 cm. From the age of 2 to puberty, children also have a peak in height growth, followed by a downward curve of elevated growth, until the epiphysis closes and stops growing. Girls’ sexual organs start to grow breasts at the age of 11; boys start to increase testicular volume and thicken their penises at the age of 13, and enter puberty.