Stable isotopes are atoms of an element that have the same number of protons but a different number of neutrons, resulting in a different atomic mass. These isotopes do not undergo radioactive decay, hence the term "stable." Stable isotopes are commonly used in scientific research, particularly in fields such as geology, biology, and environmental science, to study processes such as nutrient cycling, food web dynamics, and climate change. By analyzing the ratios of stable isotopes in samples such as rocks, water, soil, and biological tissues, researchers can gain valuable insights into the underlying processes and mechanisms at play in various systems.