Stable isotopes are variants of chemical elements that have the same number of protons but different numbers of neutrons. Unlike radioactive isotopes, stable isotopes do not decay over time, making them useful in various scientific fields. They can be found in nature and are often used in studies related to geology, environmental science, and biology. Researchers utilize stable isotopes to trace processes and understand the origins of materials. For example, in paleoclimatology, scientists analyze stable isotopes in ice cores to reconstruct past climate conditions. Similarly, in nutrition, stable isotopes help track the metabolism of nutrients in the human body.