A true-muonium only lives for two microseconds. These atoms are made up one positively and one negatively charged elementary particle, also known as muons. Although they have yet to be observed experimentally, a theoretical physicist has come up with new ways of creating them, in principle, via particle collisions.

Read more here:: http://feeds.sciencedaily.com/~r/sciencedaily/matter_energy/fuel_cells/~3/5yWcfs6bQ_A/160119111154.htm