  With latest experimental data the solar neutrino problem enters new phase
when crucial aspects of the problem can be formulated in an essentially (solar)
model independent way. Original neutrino fluxes can be considered as free
parameters to be found from the solar neutrino experiments. Resonance flavour
conversion gives the best fit of all experimental results. Already existing
data allow one to constraint both the neutrino parameters and the original
neutrino fluxes. The reconciliation of the solution of the solar neutrino
problem with other neutrino mass hints (atmospheric neutrino problem, hot dark
matter etc.) may require the existence of new very light singlet fermion.
Supersymmetry can provide a framework within which the desired properties of
such a light fermion follow naturally. The existence of the fermion can be
related to axion physics, mechanism of $\mu$-term generation etc..
