Space may look empty, but it contains extreme temperatures, high levels of background radiation, micrometeoroids, and the unfiltered glare of the sun. In addition, materials and equipment on the outside of the International Space Station are exposed to atomic oxygen (AO) and other charged particles as it orbits the Earth at the very edge of our atmosphere. Only the hardiest materials, equipment, and organisms can withstand this harsh environment, and scientists conducting research on the orbiting laboratory have identified some of them for a variety of potential uses.