From supernovae and the early condensation of the solar system, through the climate history of the planet and on to modern stratospheric chemistry, studies using stable isotopes have made a significant contribution to our understanding of the processes that shape the Earth. In this module we look at the theory and practice of isotope geochemistry, covering analytical methods and mass spectrometry, fractionation processes, and isotope behaviour in chemical cycles in the geosphere, hydrosphere, biosphere and atmosphere. The course consists of lectures, practicals, including hands-on experience in the stable isotope laboratory, and student led seminars.