The iconic image of Yellowstone is an expansive spring with rainbow-like colors radiating from its center, dominated by a fiery orange hue at its edges. Though these dazzlingly painted hot springs seem fit only for picture books, their colors come from very real, and very earthly, microscopic creatures.

Hiding out in the park’s hot springs — where temperatures are high enough to blister your skin and as acidic as liquid in a car battery — are heat-loving microbes. And they’re thriving. Where you see rings of color, there are, most of the time, rings of different bacteria, each group adapted to the conditions, such as temperature and pH (how acidic a solution is) of their environments.