Microbe is a term for tiny creatures that individually are too small to be seen with the unaided eye. Microbes include bacteria (back-tear-ee-uh), archaea (are-key-uh), fungi (fun-jeye) and protists (pro-tists). You’ve probably heard of bacteria and fungi before. Archaea are bacteria-like creatures that have some traits not found in any true bacteria. Protists include primitive algae (al-gee), amoebas (ah-me-buhs), slime molds and protozoa (pro-toe-zoh-uh). We can also include viruses (vye-rus-is) as a major type of microbe. They are the oldest form of life on earth. Microbe fossils date back more than 3.5 billion years to a time when the Earth was covered with oceans that regularly reached the boiling point, hundreds of millions of years before dinosaurs roamed the earth. Without microbes, we couldn’t eat or breathe. Without us, they’d probably be just fine.