This usually happens more suddenly in boys than in girls. Many of us get pimples during puberty on the face, back, chest, or buttocks. We get them as our skin starts growing thicker and the glands under it start making more oil. Our pores become clogged and infected. That's another good reason to wash and shampoo often.
Hormones make our bodies grow up.
Our bodies make chemicals called hormones that guide our growth into women and men - estrogen and progesterone in girls and testosterone in boys. Often we grow so fast that we feel clumsy. We even may have uncomfortable growing pains, usually in our arms and legs. Estrogen causes lots of the changes. Girls breasts begin to get fuller.