Jupiter is the largest planet in the solar system, big enough to swallow more than 1,300 Earths inside its churning atmosphere of hydrogen and helium. This episode of the Universe series looks at what makes the planet behave the way it does: bands of clouds racing at different speeds, storms larger than entire planets, and a magnetic field powerful enough to trap deadly radiation belts around it. It also spends time on Jupiter's moons, more than sixty of them, which amount to a miniature solar system of their own. Io turns out to be the most volcanically active body known, its surface constantly resurfaced by eruptions driven by the tidal pull of Jupiter's gravity. Europa gets attention for the opposite reason, an ice shell that may be hiding a liquid ocean underneath, and with it a live question about whether conditions there could support life. The film uses telescope and spacecraft imagery to move between the planet's turbulent weather and the very different worlds orbiting it.