Microbe – a living organism, also called a microorganism, that is too small to see with the unaided EYE. Most microbes are single-cell or simple multiple cell organisms. Common microbes include BACTERIA, fungi (yeasts and molds), viruses, PROTOZOA, and algae. Microbes are abundant in the natural environment as well as the environment of the human body.
Many microbes can cause INFECTION and illness in humans. Dutch scientist Antonie van Leeuwenhoek (1632-1723) identified many microbes using microscopes he constructed himself, paving the way for what would become the foundation of understanding for many disease processes.