Are most microscopic organisms harmless

Some microorganism are harmless and some are harmful,the majority of them are not enough to harm a human.

Microorganisms are, by definition, small living things. All living things need a source of food to live, and each kind of micro-organism gets/ use its food differently from another. Thus some might be harmful, and others might not.A single micro-organism might not be enough to "harm" but all micro-organisms live by the billions/trilllions. When you got an army of them, then they can cause a ignificant change on other organisms.

Any photo? or something

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