2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/204593I discuss why and how powerful is the two-detector setting in neutrino oscillation experiments. I cover three concrete examples: (1) reactor θ_{13} experiments, (2) T2KK, Tokai-to-Kamioka-Korea two-detector complex for measuring CP violation, determining the neutrino mass hierarchy, and resolving the eight-fold parameter degeneracy, (3) two-detector setting in a neutrino factory at baselines 3000 km and 7000 km for detecting effects of non-standard interactions (NSI) of neutrinos.6 pages, 3 figures, Invited talk at Fourth International Conference on Flavor Physics (ICFP2007), Beijing, China, September 24-28, 2007High Energy Physics - PhenomenologyHigh Energy Physics - Experimenttext