How does a person gain height during puberty?

During puberty the long bones, that is, the bones of the arms and the legs elongate making a person tall. The lengthening of the bone results in the gain in height. 

Many changes take place in the bodies of boys and girls during adolescence. Their shoulders become wider and chest becomes broader. Girls get developed breasts and their hips become wider. Muscles of boys grow more than the girls.

Some boys and girls have disproportionate body parts during adolescence because of the different growth rate of different body parts. The growth rate of arms and legs is higher than the other parts. The other parts soon catch up resulting in a proportionate body.

Adolescence is marked by growing of moustache and beard in boys, development of breasts in girls, start of mentruation in girls, sudden increase in height, change in voice  and growth and maturity of reproductive organs. 

(i) In boys - During adloescence the shoulders become broader and chest becomes wider. The muscles of the body grows more prominent. 

(ii) In girls -  The region below the waist becomes wider during adolescence.