How many microbes are in the human body? Your body consists of innumerable cells, but not all of them are you, exactly. In fact, more than half of what is you are microorganisms that hitch a ride on and inside your body: the average human is home to about 40 trillion microbes against 30 trillion of their own cells. And outside your body, there are trillions of times more.

The tiniest single-cell organism doesn’t even have a name yet. It’s 9 nanometers long — 150,000 of these critters fit on the tip of a hair. The largest single-cell organism in the world is a seaweed, and it can reach almost 10 feet in length! The world of microorganisms is amazing! Let’s take a look at what they are!

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