How high does Earth’s biosphere extend? Researchers have found life—in the form of microbes—as far as 32 kilometers (20 miles) into the atmosphere, capable of riding air currents around the globe. This animated short documentary explores the little-studied ecosystems high above our heads. At the outermost edge is the stratosphere, an extreme place to live by any stretch. Cold and dry, with almost no shield from radiation, the stratosphere is not unlike the surface of Mars, scientists say—and yet some organisms are able to withstand its harsh conditions. A bit closer to Earth’s surface is the troposphere, where some high-flying microbes find respite in the clouds—oases in an aerial desert. Why should we care about these tiny life forms miles above our heads? New research is beginning to reveal that some of these tropospheric residents influence the weather patterns we experience far below.