Microbes, or microorganisms, are the smallest organisms on the planet and require the use of a microscope to see them. There are a huge variety of organisms that can be classified as “microbes.” They can live alone or in colonies. They can help you or they can hurt you. These creatures make up the largest number of living organisms on the planet. There are trillions and trillions of microbes on the Earth. Microbes include bacteria, fungi, some algae, and protozoa. A microorganism can be heterotrophic or autotrophic. These two terms mean they either eat other things (hetero) or make food for themselves (auto). Think about it this way: plants are autotrophic and animals are heterotrophic. A protozoan like an amoeba might spend its whole life alone, cruising through the water. Others, like fungi, work together in colonies to survive.