Adolescent development is a period of transition from adolescence to adulthood, which lasts 6-7 years on average and can be divided into three periods: pre-puberty, mid-puberty and late adolescence. Pre-puberty is also known as the beginning of the period, boys from 12 weeks of age, girls from 10 years old; mid-puberty is also known as the rapid growth period, as the name suggests, during this period the child height growth is more obvious, boys from 14-16 years old, girls from 11-13 years old; late adolescence is also known as slow growth period, boys after 16 years old, girls after 13 years old. Generally speaking, puberty development lasts until 18-20 years old for boys and 16-18 years old for girls. 1, physical changes during puberty, boys grow about 28cm in height, girls about 25cm, but because boys start puberty later than girls, the end of time later than girls, resulting in pre-pubertal starting height higher than girls, long puberty cycle, and during puberty boys per growth rate faster than girls, so the final height of men than women about 10-13 cm higher. There is a time difference in the sudden increase in length of various body parts, with limbs preceding the trunk, lower limbs preceding upper limbs, and distal limbs preceding proximal ones. During puberty, androgens mainly promote protein synthesis and stimulate cartilage proliferation in the scapular belt, resulting in taller, wider shoulders and more muscular males; in females, estrogen mainly promotes fat synthesis and stimulates cartilage proliferation in the pelvic belt, resulting in shorter, wider hips and fuller bodies in females. However, as youth development progresses, when estrogen increases to a certain degree, it can cause early epiphyseal closure, resulting in the loss of growth space for children and affecting the final height. 3. Sexual characteristics development Male development starts from about 12 weeks old, firstly manifested as testicular enlargement, when beard, throat knot and voice change appear, and the first ejaculation occurs around 15 years old, marking the maturity of sexual development; female development starts from about 10 years old, firstly manifested as breast development, and the first menstruation occurs around 13 years old, marking the maturity of sexual development in late adolescence. This is a sign of sexual maturity.