Believe it or not, nearly a mile underground, life thrives. These organisms live in communities called biofilms inside the rock and water that accumulates underground. Scientists want to know more about how they survive. For example, what do they eat? How do they breathe? Many absorb minerals as food and oxygen. We know that most organisms can’t live in these conditions, yet communities of biofilms thrive in the extreme conditions of the thermal pools at Yellowstone, the polar ice caps, deep sea ocean vents, and Sanford Lab. That’s why we call them extremophiles.