For information on a specific unit, click on the first letter of its name: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z. Answers to the three most frequently asked questions:
Microorganisms were the first living creatures on earth. It is estimated there are a total of 5 nonillion microorganisms on earth (5x1020). You will find nearly 10 million a millilitre of ocean water and 40 million in a gram of soil. They are also ubiquitous on the human body.
An organism that is microscopic or submicroscopic, which means it is too small to be seen by the unaided human eye. Supplement. Microorganisms were first observed by Anton van Leeuwenhoek in 1675 using a microscope of his own design. Examples of microorganisms include bacteria, fungi, archaea, and protists.