Meson is a subatomic particle which is intermediate in mass between an electron and a proton and transmits the strong interaction that binds nucleons together in the atomic nucleus.Meson is composed of one quark and one antiquark which are bound together by the strong interaction.Because mesons are composed of sub-particles,they have a physical size with a diameter roughly one fermi which is about 2⁄3 the size of a proton or neutron.All mesons are unstable,with the longest-lived lasting for only a few hundredths of a microsecond.Charged mesons decay to form electrons and neutrinos,while uncharged mesons may decay to photons.