‘The making of magma’ discusses the formation of magma. Volcanism is driven by prodigious amounts of heat from deep inside the Earth that partly melts rock to form magma, which accumulates and evolves deep underground, and may drive powerful eruptions that expel ash and lava on to the surface, creating a volcano. This process can be studied by inferences based upon volcano behaviour, seismic information, chemical tracers in volcanic materials, experimentation, and other clues. From enormous, diffuse networks deep in the Earth, the magma rises and gathers together in the crust as a complex system of interconnected fractures, reservoirs, and conduits. These magma reservoirs can be detected by seismic imaging.