When you think about life on Earth, you probably think of many living things. Plants, mammals, insects, and reptiles are all a part of life on Earth. We think of these things because they are the things that we see. Want to know something amazing? These creatures make up only a small part of all living things on Earth. "Where are the rest of them?" you might ask. They are here. They are all around us- on us, inside us, everywhere. Most of the living things on Earth are so small that they can only be seen under a microscope. What kinds of living things are so small that we cannot see them? There are many: tiny plants called algae, some kinds of molds and fungi, and bacteria (or germs). These are only a few of the organisms that make up life under a microscope.
Bacteria are one kind of microorganism. They are very, very small. Hundreds of thousands of bacteria can fit into a space the size of the period at the end of this sentence. Bacteria are everywhere! They are in the ground. They are in our homes. Bacteria are on the food that we eat. They are even inside our bodies! Most people think bacteria are bad .....