Tritium is a radioactive isotope of hydrogen, symbolized as ³H. It contains one proton and two neutrons in its nucleus, making it heavier than regular hydrogen, which has no neutrons. Tritium is naturally produced in the atmosphere when cosmic rays interact with nitrogen. It is also generated in nuclear reactors. Tritium is used in various applications, including nuclear fusion research and as a luminous material in watch dials and exit signs. Due to its radioactive nature, tritium emits low-energy beta particles, which are not harmful to humans unless ingested in large quantities.