Microorganisms are extremely small life forms, so small in fact that we cannot even see them with our naked eyes. Micro refers to one millionth part of a meter and these organisms are about that size (couple of order of magnitudes smaller or larger as well). Microorganisms include bacteria, protozoa, viruses, fungi, etc. We typically use microscopes to take a look at them.
Microorganisms evolved billions of years ago on Earth and are precursors to higher life forms like us. Microorganisms are both beneficial and harmful to us. There are a number of bacteria, such as lactobacillus (which help in formation of yogurt or curd) that are useful to our life. Similarly, there are a number of microorganisms such as (strains of) E. coli that are pathogenic (cause diseases) to us. We can also engineer microorganisms to behave in a certain fashion and use them for production of chemicals or cleanup of organic matter from wastewater.
A microorganism is a living thing that is much to small for the naked eye to perceive without the use of a microscope. Microorganisms play an important role, for example some microorganisms are responsible for the breakdown of nutrients into smaller components. Soil bacteria, nematodes, and protozoa are a few examples of microorganisms that are necessary for the health of our soil. Microorganisms are also important for the overall health of the human gastrointestinal track.
Microorganisms are small living beings which cannot be seen by the naked eye.
Microorganism are any living thing (organism) that is too small to be easily seen by the unaided human eye. Microorganisms are generally observed using a Microscope.
Bacteria (germs) some fungi and some protist are considered microorganisms