Your emotions are changing, your attitudes are changing and even the way you think is changing. It's all very normal at this time in your life. You're changing socially, as well. You no longer expect your parents to make all of your decisions for you. 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.