What is microorganisms?

Microorganisms also known as microbes. Microorganisms are living things which are so small that they cannot be seen with the naked eye and are only visible under the microscope.

Who discovered the first microorganism?

Anton Van Leewenhoek (1632-1732) was the first person to discover the existence of microorganisms, when he used the simple microscope that he himself invented to view a drop of rainwater which he collected from his roof.