  Neutrino oscillations in matter can exhibit a specific resonance enhancement
-- parametric resonance, which is different from the MSW resonance.
Oscillations of atmospheric and solar neutrinos inside the earth can undergo
parametric enhancement when neutrino trajectories cross the core of the earth.
In this paper we review the parametric resonance of neutrino oscillations in
matter. In particular, physical interpretation of the effect and the prospects
of its experimental observation in oscillations of solar and atmospheric
neutrinos in the earth are discussed.
