Histological examination reveals the first evidence of spermatogenesis between eleven and fifteen years of age. Sperm can be found in early- morning voided urine specimens at a mean chronological age of 13.3 years, and the first conscious ejaculation occurs at a mean of 13.5 years of bone age (14.5 years of chronological age). Thus, the average age of onset of sperm formation occurs between stages 2 and 3 pubic hair or genital development, indicating that the achievement of fertility precedes the achievement of adult physical development.
