  The program of reconstruction of the neutrino mass and flavor spectrum is
outlined and the present status of research is summarized. We describe the role
of future solar and atmospheric neutrino experiments, detection of the Galactic
supernovae and double beta decay searches in accomplishing this program. The
LSND result and four neutrino mass spectra are considered in connection with
recent searches for the sterile components in the solar and atmospheric
neutrino fluxes.
