A microbe or microorganism is any living thing that’s too small to see without a microscope. That includes protozoa, viruses, fungi, bacteria and others. They can both help and hurt human beings.
Microbes have been around for at least 3 billion years and outnumber all visible life forms on planet earth by a factor of 100 million.
For every cell in the human body, there are approximately 1.3 microbial cells. In other words your 30 trillion human cells are accompanied by 40 trillion microbes.
We have evolved with each other, in a deeply complex, symbiotic relationship. Microbes train our immune systems, help us digest our food, and even help us fight disease.
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