Adolescence, also known as puberty, is the transition period from childhood development to adulthood. The World Health Organization (WHO) defines the age range of puberty as 10-19 years. In our country, the overall age range of 10-24 years is usually considered in terms of physiological, psychological and social adaptability development and maturity and when it comes to adolescent health care. Adolescence is the second peak of human growth and development, with great physiological changes, rapid growth in height and weight, and the increasing maturity of various organs such as heart, lungs and liver functions, with various indicators reaching or approaching adult standards. Sexual organs are the last to develop in the human body, and puberty is the period of rapid development and maturity of sexual organs in terms of form and function. Once the sexual organs are mature, it is a sign that all the organ systems in the body have matured. From the perspective of medical physiology, puberty can be roughly divided into three developmental stages as follows: (a) Early puberty. The most obvious external changes in adolescents during this period are accelerated growth and sudden increase in height. At this time, the average annual growth in height is 8 cm, and even 10-13 cm; at the same time, the weight also increases by 5-6 kg, and as much as 10 kg. At the same time, the genitalia in the body is quietly developing. However, menstruation does not occur in girls and spermatorrhea does not occur in boys. (B) Middle puberty. The rapid development of secondary sexual characteristics is the main feature of this period, which is more striking. When women are 9-10 years old, their breasts begin to develop, which is the first secondary sexual characteristics of young girls and a sign of puberty; at the age of 11, pubic hair appears; at the age of 12-13, the nipple areola continues to increase in size, but still blends in with the whole breast outline; pubic hair continues to increase and develop toward the pubic mound and the middle of the abdominal wall, from fine to thick, and the pigment gradually settles. After the age of 13 (some girls earlier), the girl has her first menstrual period, but it is generally irregular. During the first 12 years, the ovaries are not yet functional or mature enough to ovulate; at the same time as the menarche or a little later, the axillary hair grows out and the pubic hair shows a feminine inverted triangular distribution with the bottom side parallel to the level of the pubic symphysis; the glands in the areola area develop and form a second bulge on the already full and enlarged breasts. In males, throat knots, voice change, beard, pubic hair and axillary hair grow, and seminal emission and other physiological phenomena have occurred. (iii) Late puberty. About 14-15 years of age, women can present regular ovulatory menstruation; breast development is mature, nipples protrude on the contoured breasts; at the age of 16-17, development approaches maturity, bone scale heals, and height growth basically stops. During this period, sex organs are basically mature in terms of form and function, male and female gonads basically have the function of producing and providing sex hormones to the body, female ovaries can discharge mature eggs, male testicles can produce viable sperm, and secondary sex characteristics have basically developed as adults. The development of the above sexual characteristics has a clear timing and sequence. If there is a temporal violation, such as breast development before 8 years old or menstruation before 10 years old, it is precocious puberty; if the development starts after 16 years old, it is called delayed puberty; if the development remains childish after 18 years old, it may be incomplete sexual development. Idiopathic precocious puberty, true precocious puberty caused by brain lesions, pseudo-precocious puberty caused by misuse of estrogen-containing drugs and foods and ovarian tumors, congenital disorders and ovarian hypofunction delayed by gonadotropins, etc. must be promptly investigated and treated. The disorder of sexual development should be paid more attention to, such as menstruation before breast development and pubic hair, or premature growth of axillary hair and pubic hair before breast development, are abnormal performance, and should be promptly referred to the doctor. In addition, adolescent women are also prone to irregular periods, secondary amenorrhea, dysmenorrhea, premenstrual syndrome (PMS), abnormal leucorrhea, etc. If your child has any of these conditions, please go to our Women’s Health Department – Adolescent Health Clinic in time for consultation and guidance from our experts.