The sexual organs of boys develop around 12 weeks of age, and it is abnormal if children develop their sexual organs too early or too late. If a boy’s sexual organ development occurs before the age of 9 years, it is a case of premature development. If a boy’s sexual organ development does not occur beyond the age of 15, it is considered delayed development. The development of sexual organs in boys is mainly the enlargement of testicles and the growth and thickening of the penis. As the sexual development of children progresses, there will also be the appearance of armpit hair and pubic hair, as well as the appearance of throat knots, voice changes, and even seminal emission.