Abstract: The search for neutrino-less double beta decay (NLDBD), an extremely rare decay process of certain nuclei, is being actively pursued by particle and nuclear physicists. A discovery would confirm that neutrinos are their own anti-particle, i.e. Majorana fermions. This decay also violates the conservation of lepton number and provides a viable explanation for the matter-antimatter asymmetry of the early universe. Around the world, many collaborations utilize different detector techniques to search for this rare process beyond the Standard Model of particle physics in different isotopes. No positive signals have been identified so far and the half-life limit of NLDBD has been set to at least 10²⁶ years. Recently a series of R&D projects have started in China, which hopefully will evolve to one or two future ton scale NLDBD experiments in the near future.