The testes of adolescent boys generally begin to develop between the ages of 10 and 14 years, and their specific structure consists of the seminiferous tubules with surrounding connective tissue, whose main function is to produce sperm and secrete androgens. Upon entering puberty, the testes and scrotum enlarge rapidly, and the length and curvature of the seminiferous tubules increase rapidly. The structure of the testis undergoes significant changes, and lumens of the seminiferous tubules, which are gradually connected to the testicular network and to the output tubules, begin to appear. As spermatogonia are activated, they begin meiosis and multiply to become spermatogonia of all stages. As the mesenchymal cells transform into the mature type, they begin to secrete androgens, and secondary sexual characteristics such as penile growth, thickening, beard and axillary hair growth, and a lowered voice begin to appear. The seminal vesicle glands and prostate glands also mature along with the development of the testes and begin to secrete fluid, and spermatozoa are gradually produced.