Micro-organisms, or microbes, are a diverse group of minute, simple forms of life that include bacteria, algae, fungi, protozoa, and viruses. Microorganisms are too small to be seen with the naked eye and are normally viewed by means of a microscope. The study of microorganisms is called microbiology.
"Microorganism." Britannica School. Encyclopedia Britannica, Inc., 2017. Web. Oct 24 2017