  We review our theoretical approach to neutral current photon emission on
nucleons and nuclei in the few-GeV energy region, relevant for neutrino
oscillation experiments. These reactions are dominated by the weak excitation
of the $\Delta(1232)$ resonance but there are also important non-resonant
contributions. We have also included terms mediated by nucleon excitations from
the second resonance region. On nuclei, Pauli blocking, Fermi motion and the
in-medium $\Delta$ resonance broadening have been taken into account for both
incoherent and coherent reaction channels. With this model, the number and
distributions of photon events at the MiniBooNE and T2K experiments have been
obtained. We have also compared to the NOMAD upper limit at higher energies.
The implications of our findings and future perspectives are discussed.
