In particle physics, mesons ( or ) are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a diameter of roughly one fermi, which is about 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 (sometimes through intermediate particles) to form electrons and neutrinos. Uncharged mesons may decay to photons.

Mesón Group is a Cambrian sedimentary formation located in the Argentine Northwest and nearby parts of Bolivia. The group members ret unconformably on top of the Ediacaran–Cambrian Puncoviscana Formation. According to G.F. Aceñolaza the Mesón Basin –the sedimentary basin that oroginated the Méson Group– lied between Arequipa Craton and Río de la Plata Craton.