The earliest feature of male development is the development of the testes. Once the testes are formed during fetal life, they can secrete androgens to regulate the development of the sex organs. After birth and until the age of 10, this stage grows very slowly, and further development begins in the prepubertal period. In boys, the development of testes is the first sign of puberty, and the androgens secreted by them can promote the emergence of secondary sexual characteristics. 10-11 years old, the penis starts to enlarge, and the foreskin mostly covers the glans when young; 8-10 years old, the foreskin is turned up; 12-13 years old, pubic hair starts to appear; at the age of sexual maturity (12-15 years old), mature sperm starts to appear, and the first ejaculation occurs when the volume of testes reaches 6 ml. The first ejaculation occurs at the age of 14-15 years; armpit hair appears at the age of 14-15 years, the voice becomes thicker; after the age of 16 years, the beard is able to grow, acne and throat knots appear, and further muscle development occurs.