Protium, tritium, and deuterium are isotopes of hydrogen with distinct applications. Protium, the most common form of hydrogen, is widely available as a gas. Deuterium, often found in heavy water (D2O), is utilized in nuclear reactors as a moderator and in spectroscopy, particularly NMR. Tritium, a radioactive isotope, is significant in nuclear fusion research and is also used in glow-in-the-dark products like wristwatches. However, purchasing tritium typically requires a license due to its radioactive nature. While chemical supply companies may sell isotopes, they primarily cater to academic, industrial, and government clients. Tritium has been used in biochemical research as a radiolabel for tracking metabolites, though its current prevalence in research is uncertain.