Hypothetical way of cold fusion, in which the electron in the hydrogen atom is replaced by a much heavier muon, and thanks to this, the hydrogen nuclei can fuse even at room temperature. The muon is a subatomic particle similar to the electron, but 207 times heavier. Its half-life is a few microseconds. If we inject a muon into a mixture of deuterium and tritium, the muon can be trapped by an ion, forming a muon atom that can bond with another hydrogen nucleus. The muon D-T molecule will have the nuclei close enough together that fusion can occur. In this process, the muon is released and can serve as a catalyst for the next fusion. We do not yet have a suitable and cheap source of muons to carry out this type of fusion.