  Even after the discovery of neutrino flavour oscillations, based on data from
atmospheric, solar, reactor, and accelerator experiments, many characteristics
of the neutrino remain unknown. Only the neutrino square-mass differences and
the mixing angle values have been estimated, while the value of each mass
eigenstate still hasn't. Its nature (massive Majorana or Dirac particle) is
still escaping. Neutrinoless double beta decay ($0\nu$-DBD) experimental
discovery could be the ultimate answer to some delicate questions of elementary
particle and nuclear physics. The Majorana description of neutrinos allows the
$0\nu$-DBD process, and consequently either a mass value could be measured or
the existence of physics beyond the standard should be confirmed without any
doubt. As expected, the $0\nu$-DBD measurement is a very difficult field of
application for experimentalists. In this paper, after a short summary of the
latest results in neutrino physics, the experimental status, the R&D projects,
and perspectives in $0\nu$-DBD sector are reviewed.
