The scientists who study mini life-forms are called microbiologists.
They know a lot about microbes. But they don’t know exactly when or how microorganisms first showed up on Earth. Maybe microbes hitched a ride to Earth on a meteor. Maybe some proteins—the building blocks of life—formed in a bubbling pool of water and came together to form the earliest microbes.
Nobody knows for sure what happened, but microbes did develop. They had a formula for success. Each creature had a genetic blueprint, or code, so it could make a copy of itself.
To spread all over the Earth, the microbes divided and multiplied. Under the right conditions, a microbe can split in half every 20 minutes. In ten hours, one microbe might become a billion microbes!
Scientists have now identified a huge amount of different types of microbes. There are so many, microbiologists have organized them into categories. Four of them are shown below.
