he high energy frontier at the LHC may provide an answer to the question of neutrino mass origin. A paradigmatic example is the Left-Right symmetric theory with heavy Majorana neutrinos. We review the existing status of collider searches for lepton number violating signals at the LHC. In order to fully realize the potential coverage for such particles, both prompt and displaced signals ought to be considered. These arise either from the extended gauge sector or from additional scalars that may mix with the Higgs and lead to exotic, potentially displaced, lepton number violating decays. These offer a direct insight to spontaneous mass origin of neutrinos, in complete analogy to the SM fermions.