We live in a time of unprecedented scientific knowledge about the origins of life on Earth. But if we want to grasp the big picture, we have to start small—very small. That’s because the real heroes of the story of life on Earth are microbes, the tiny living organisms we cannot see with the naked eye. Microbes were Earth’s first lifeforms, early anaerobic inhabitants that created the air we breathe. Today they live, invisible and seemingly invincible, in every corner of the planet, from Yellowstone’s scalding hot springs to Antarctic mountaintops to inside our very bodies—more than a hundred trillion of them. Don’t be alarmed though: many microbes are allies in achieving our—to say nothing of our planet’s—health.
