Many of the key processes that operate in the Earth today—and have shaped its evolution over geological time—involve highly mobile and reactive amorphous materials: metallic, silicate, and carbonate melts, as well as volatile-rich supercritical fluids and brines. Constraining the properties of these disordered systems is crucial for understanding the magma ocean from which the mantle crystallised, ongoing magmatic differentiation, volatile cycling, mineralisation, and rock–fluid reactions such as serpentinization, a key source of white hydrogen. Yet studying materials that lack long-range order is inherently challenging: they typically exist only at high temperatures, often scatter X-rays weakly, and are difficult both to contain at the pressures relevant to planetary interiors and to probe in situ, where meaningful data can be obtained. This talk will explore recent work at Bristol on amorphous materials under extreme conditions, spanning metallic, silicate, and carbonate melts, as well as volatile-rich supercritical fluids and brines, and their roles in mineral–fluid interactions. I will discuss the experimental, computational, and analytical approaches we use to capture, contain, and interpret these materials, and what they reveal about our dynamic planet.