An organism that is microscopic.

An organism that is too small to be visible without the aid of a microscope. ( micro-organisme)

any organism not visible to the naked eye, for example, bacteria.

A very small organism which can only be seen with a microscope or an electron microscope. Under the generic term 'micro-organisms' one finds bacteria, viruses, microscopic fungi, protozoa and some parasites.

Microscopic organisms, including bacteria, viruses and fungi. Some are capable of causing disease in humans and animals.

A living thing that can be seen only with magnification, such as bacteria and viruses.

Any small organisms that can only be seen with a microscope.

A living organism which is too small to be seen with the naked eye and can only be observed using a microscope. Includes bacteria and most protists.

An organism that can be seen only under a microscope, usually, an ordinary light microscope. It includes bacteria, mycoplasm, yeasts, single-celled algae and protozoa. Multicellular organisms are normally not included, nor fungi apart from yeasts. Viruses are also not automatically included, as many scientists do not classify them as organisms.

A small organism such as bacteria that can only be seen using a microscope.