Caption: Cells in normal human blood
Your body has many different parts. You have hard bones. You have muscle. You have a brain, a stomach, and a heart. Your body needs all these parts to work properly.
Think about the different parts of your body. Your eyes, arms, and toes are very different from each other. Yet they are all alike in one way. All the parts of your body are made of cells. Cells are the smallest part of a living thing. They are called the building blocks of the body.