You're probably starting to ask more questions and pose more challenges. Teenagers develop at different rates. Some start to mature early on, others take longer to grow and mature. This time in your life is known as puberty. Puberty is simply defined as the biological changes of adolescence.
Body composition begins to change.
The circulatory and respiratory systems begin to change. The growth spurt usually triggers the feet and legs to grow, followed by the body's trunk and ending in the shoulders and chest. Bones become harder and more dense, while muscle and fat contribute to an adolescent increase in weight. Sexual development involves enlargement, maturity and the reproduction of the primary sex organs. For boys, the testes begin to produce part of the fluid for sperm cells and the prostate gland to produce semen.