In boys puberty starts near 14-15 years of age. During this phase testosterone level spikes and is responsible for all the changes which are,

• Body is larger, more muscular, and stronger.

• Beard, moustache and chest hairs start appearing.

• Shoulders become broad.

• Voice becomes low pitched.

• Behavior becomes a little aggressive because of a spike in testosterone levels.

• Development of Adam's apple is there.

• Enlargement of the penis and appearance of pubic hairs.