  The status of the search for neutrinoless double beta decay is reviewed. The
effort to reach the sensitivity needed to cover the effective Majorana neutrino
mass corresponding to the degenerate and inverted mass hierarchy is described.
Various issues concerning the theory (and phenomenology) of the relation
between the $0\nu\beta\beta$ decay rate and the absolute neutrino mass scale
are discussed, in particular the issue of mechanism of the $0\nu\beta\beta$
decay. Finally, the relation between the neutrino magnetic moments and the
charge conjugation property (Dirac vs. Majorana) is described.
