Microorganisms
Microorganisms, or microbes, are microscopic organisms that are too small to be visible to the naked eye. The study of microorganisms deals with microbiology. Microorganisms can be bacteria, archeas, fungi or some other eukaryotes, but not viruses or prions, because the latter are generally classified as inanimate, although microbiology also studies these objects. Microorganisms are often described as single-celled organisms; however, some unicellular bacteria or prostatitis are visible to the naked eye, and some multicellular species are microscopic.