True muonium is yet to be observed experimentally, though it may have been produced in experiments involving collisions of electron and positron beams. The ortho-state of true muonium (i.e. the state with parallel alignment of the muon and antimuon spins) is expected to be relatively long-lived (with a lifetime of 1.8 × 10 s), and decay predominantly to an e e pair, which makes it possible for LHCb experiment at CERN to observe it with the dataset collected by 2025.