All living things—from bacteria to animals—are made up of cells. Bacteria are single-cell organisms and among the oldest and tiniest life forms on the planet. Even though one bacterial cell is so small that we can only see it through a microscope, it is a complete organism, equipped with everything it needs to survive. A single bacterium consumes nutrients, grows up, and reproduces right under our noses in its microscopic world. Let’s take a closer look at a bacterial cell. The cell is like a little factory that processes nutrients into materials it needs to survive and to grow.