From a planet with a hexagonal storm to the home of the Solar System's largest volcano, our neighbouring bodies are unique and fascinating places. Where else would you find somewhere with days longer than its years? Humanity's understanding of planets has changed drastically since ancient times when early astronomers mistook the lights they saw in the sky for wandering stars. We've come a long way since then, but there's still so much we don't know. Could there be life on Mars? How many planets exist outside the Solar System? Is there another 'Earth' out there? And why can't we call Pluto a planet anymore? Discover more in this essential guide to planets in the Solar System and beyond by astronomer Dr Emily Drabek-Maunder of Royal Observatory Greenwich.