Microbiologists, the scientists who study mini life-forms, know a lot about microbes.
But they don’t know exactly when or how microorganisms first appeared on Earth. Maybe microbes hitched a ride to Earth aboard 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 developed—and had a formula for success. Each creature contained a genetic blueprint, or code, that allowed it to make a copy of itself.
To spread themselves to all parts of 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 develop into a billion microbes!
There are so many different types of microbes now that microbiologists have organized them into categories. Four of them are shown below.
