The gas giant jupiter, the largest planet in our solar system, is a world of extreme weather and powerful magnetic fields. Its four largest moons, io, europa, ganymede, and callisto, are dynamic, geologically active worlds that challenge our understanding of how planets and moons form. Through the lens of space missions like galileo, we explore the mysteries of this enigmatic system, from the volcanic activity on io to the potential for a subsurface ocean on europa, and the strange, cratered landscape of callisto.