Neutrino oscillation experiments measure the flavor and energy of the detected neutrinos from the products of their scattering in
detectors. Unfortunately, nature has required that precision accelerator oscillation experiments seeking to discover CP violation in
neutrino mixing and to uncover the ordering of neutrino masses must operate at ~ 1 GeV energies where nuclear effects are important and where a frustrating variety of final states must be reconstructed. I’ll review what we have learned about this thorny problem in recent years, and how what we have learned has impacted neutrino oscillation measurements. I’ll focus largely on the MINERvA experiment at Fermilab which is currently wrapping up its final results.