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 came to Earth. Maybe they hitched a ride here on a meteor. Maybe some proteins, the building blocks of life, formed in a pool of water. They might have come together to form the earliest microbes.
Nobody knows for sure how they got here. But microbes had a recipe for success. Each creature had a genetic blueprint, or code, inside it. The code let the microbe make a copy of itself.
To spread all over the Earth, the microbes split up. That’s how they became so plentiful. In the right conditions, a microbe can split in half every 20 minutes. In ten hours, one microbe might become a billion!
Today, scientists know about a huge number of different microbes. There are so many, scientists organized them into categories. Four of them are shown below.
