what is a microorganism

Microorganisms, also known as microbes, are organisms of microscopic size that can exist in their single-celled form or as a colony of cells. They are too small to be seen by the naked eye and can only be observed with a microscope. Microorganisms can be bacteria, fungi, archaea, or protists. They are essential to many aspects of life on Earth, including food production, waste treatment, and maintaining soil fertility. Microorganisms are also useful in creating biofuels, chemicals, and enzymes, and are invaluable in research as model organisms. However, some microorganisms can make us sick, and they have been weaponized and used in warfare and bioterrorism.