Conditions that occur during development are clinically called manifestations, not symptoms. At the age of 11 to 12 years old, boys will experience height development, sex organ development and body hair development. 1. Height development: Boys usually enter the developmental stage around the age of 11 to 12 years old, and there will be a stage of rapid growth in height, at this time, the height will grow rapidly, and the weight will also increase. 2. Sexual organ development: after entering the developmental period, boys will appear sexual organ development, with age, the boy’s testicles gradually become larger, the penis will also gradually grow, darker color. Some boys will also experience spermatorrhea and other physiological states. 3. Body hair development: 11 to 12-year-old boys will also appear body hair changes, boys will gradually begin to appear fine pubic hair. With the passage of time will also appear armpit hair growth and lip growth of beard and so on. Some boys develop acne with the secretion of male hormones. Boys in the developmental period will also appear voice changes, in the developmental period to strengthen the nutrition, to avoid malnutrition, affect the development.