Adolescence is the period of reproductive maturity which lies usually between the ages of 10 to 18 years .
The causes are differ from boys to girls .
In girls :
1) Breasts begin to develop .
2) Hair grows in the armpits and genital region .
3) Reproductive phase of life begins .
4) The first menstrual cycle begins termed as 'menarche' .
In boys :
1) Facial hair , moustache and beard begin to grow .
2) Hair starts growing on the chest .
3) Hair grows in the armpits and the genital region .
4) Reproductive phase of life begins .
5) Change in the voice , growing tall , pimples on the face are some changes .