What Is Inside?

Imagine you could peek inside your body. What would you see? Bones and blood? A beating heart? Yes. But there is more. Much more! Long ago, people could only guess at the inner workings of the human body. The invention of the microscope helped to change that. It allowed scientists to examine bits of the body in detail. One of the first things they discovered was that our bodies are made of tiny parts called cells.

Millions of Cells

The microscopic amoeba that oozes along the pond floor has only one cell. Bigger creatures, such as beetles, have tens of thousands of cells. All plants and animals are made of many cells.

Your body has millions and millions of cells, but they’re not all the same. There are bone cells, blood cells, brain cells, and cells for every part of your body. Each kind of cell has a certain job to do. Groups of different kinds of cells that work together to perform a specific job are called organs. Your stomach and your heart, for example, are two organs in your body.

Organs that work together form a system. Your body has many systems. Each system performs one major job, such as breathing or moving. The systems in your body work to keep your body active and strong.

A white blood cell

Red blood cells

A microscope allows scientists to see very small things.