Isotope geochemistry is a field of study that focuses on the investigation of the isotopic composition of elements in Earth materials, such as rocks, minerals, and fluids. Isotopes are different forms of an element that have the same number of protons but different numbers of neutrons, resulting in variations in atomic mass. By measuring the ratios of different isotopes within a sample, researchers can gain insights into geological processes such as the formation and evolution of rocks, the cycling of elements within the Earth's system, and the interaction between different reservoirs of materials, such as the atmosphere, hydrosphere, lithosphere, and biosphere. Isotope geochemistry is used in a wide range of applications, including dating rocks and minerals, tracing the sources of materials, investigating past climatic conditions, and understanding natural processes in the Earth's interior and surface environments.