The Geochemistry group uses chemical techniques to understand natural processes on a range of temporal and spatial scales, from nano-scale pre-solar grains in meteorites, to the biogeochemistry of oceans past and present, to the large-scale chemical structure and formation of planets. The remit extends from primordial processes in the Earth’s deep interior to interactions of hydrosphere, cryosphere and atmosphere, with implications for future climate. A major theme is the use of isotopic tracers to understand the nature and chronology of cycling between the major reservoirs of the Earth. These skills also allow us to monitor environmental pollution, not least from anthropogenic nuclear fission.