The testicles continue to increase in size and the penis begins to increase in circumference as well as in length. Growth of underarm and facial hair increases and shaving may begin. The internal reproductive organs mature enough to produce the first ejaculation of semen and sperm. Sometime between ages 14 and 18. The body nears its final adult height and the genitals achieve their adult size and shape.
Pubic hair spreads to the thighs and upward towards the stomach.
Chest hair appears. Shaving becomes more frequent as facial hair reaches its full growth. Height, body hair, muscle growth and strength continue to increase into the twenties for some young men. Males, like females, experience increased sexual desires, dreams, fantasies and arousal during puberty. As a male becomes sexually excited, his penis fills with blood and gets hard and erect.