Moons come, quite literally, in all shapes and sizes. Our Moon is just one of more than 200 moons in the Solar System that we've identified so far. Scientists have discovered moons made of rock, others of ice. There are moons with atmospheres or with oceans hidden beneath their surfaces, and even some with active volcanoes. Others could perhaps be suitable for life! Astronomer Anna Gammon-Ross of Royal Observatory Greenwich travels through the Solar System, hopping from one moon to the next, to discover not only what these natural satellites have in common, but also what makes each one unique. Learn about the moons that can be found in and around Saturn's rings (and the many others we suspect there could be), the objects orbiting the distant dwarf planets and the curious theory of moon-moons.