What are microbes?

Microbes, also called microorganisms, are living agents that are too small to be seen with the unaided eye. They include bacteria, archaea, many fungi, protozoa, and microscopic algae. Viruses are generally not considered to be living organisms, since they cannot reproduce independently; however, they are often studied alongside microbes because of their incredibly small size and their interactions with living cells. Microbes are among the oldest and most abundant forms of life on Earth. They...