Radiogenic isotopes are isotopes that are formed through the radioactive decay of parent isotopes. These isotopes are commonly used in geochronology, the study of the age and history of rocks and minerals. By measuring the ratios of radiogenic isotopes to their stable isotopes in a sample, researchers can determine the age of the sample and gain insights into geological processes such as the formation of rocks, the movement of tectonic plates, and the evolution of Earth's crust. Radiogenic isotopes are also used in other fields such as environmental science, archaeology, and forensic science.