  We review the current status of the neutrino mass and mixing parameters
needed to reconstruct the neutrino mass matrix. A comparative study of the
precision in the measurement of oscillation parameters expected from the next
generation solar, atmospheric, reactor and accelerator based experiments is
presented. We discuss the potential of $0\nu\beta\beta$ experiments in
determining the neutrino mass hierarchy and the importance of a better
$\theta_{12}$ measurement for it.
