Delightful diversty

A microorganism or microbe is an organism that is microscopic (too small to be seen by the human eye). The study of microorganisms is called microbiology. Microorganisms include bacteria, fungi, archaea or protists, but not viruses and prions, which are generally classified as non-living. Most microorganisms are single-celled, or unicellular, but some are microscopic, and some unicellular protists are visible to the average human.
Microorganisms live almost everywhere on Earth where there is liquid water, including hot springs, on the ocean floor, and deep inside rocks within the Earth's crust. Microorganisms are critical to nutrient recycling in ecosystems as they act as decomposers. As some microorganisms can also fix nitrogen, they are also an important part of the nitrogen cycle. However, pathogenic microbes can invade and grow within other organisms and cause diseases that kill millions of people and other animals every year.