In China, the age range from 12 to 18 is generally considered as puberty. Adolescence is the second peak of human growth and development, with great changes in physiology, rapid growth in height and weight, increasingly mature functions of heart, lungs, liver and other organs, and various indicators reaching or approaching adult standards. Under normal circumstances, girls' puberty is about one year earlier than boys', and it takes about 2 ~ 3 years from the beginning of breast development to menarche, and then armpit hair and pubic hair grow out, the pelvis becomes bigger, and the subcutaneous fat of the whole body increases (especially in the chest and shoulders), forming a plump posture of women. The boy has a long beard, prominent Adam's apple, deep voice and solid musculoskeletal development, forming a burly physique of a man. With the sexual development of adolescence, the sexual psychological development of young friends has also made a qualitative leap. The development characteristics of their sexual consciousness and behavior during this period are: from Russian origin to clarity, from poverty to prosperity, from naivety to maturity.
Adolescence is the golden age of life. Young friends should seriously study scientific knowledge, be familiar with their own changes, be psychologically prepared, deal with heterosexual relations, and pay attention to physical exercise and nutrition in order to spend this wonderful time smoothly.