Deuterium labeling is a technique used in scientific research to track the movement or transformation of molecules within a system. Deuterium is a stable isotope of hydrogen that can replace hydrogen atoms in organic molecules without significantly altering their properties. By incorporating deuterium into a molecule, researchers can use techniques like nuclear magnetic resonance spectroscopy or mass spectrometry to trace the pathway of the labeled molecule in biological systems, chemical reactions, or materials. This approach is particularly useful for studying metabolism, protein folding, drug metabolism, and other dynamic processes. Deuterium labeling can provide valuable insights into the behavior of complex systems and help unravel intricate molecular mechanisms.