  The neutrino mass generation mechanism, the nature of dark matter and the
origin of the baryon asymmetry of the Universe are three compelling questions
that cannot be accounted for in the Standard Model of particle physics. In this
thesis we focus on all these issues by providing a possible solution in terms
of a minimal extension of the Standard Model, consisting in the addition of a
set of sterile fermions to the field content of the theory. Sterile fermions
are gauge singlet fields, that can interact via mixing with the active
neutrinos. We focus on the Inverse Seesaw mechanism, which is characterised by
a low (TeV or lower) new physics scale and that can be tested in current and
future experimental facilities. We present the model building analysis that
points towards the minimal realisations of the mechanism, and the
phenomenological study in order to accommodate light neutrino masses and to
impose all the relevant experimental constraints in the model, as well as the
expected experimental signatures. We show the viability of the sterile neutrino
hypothesis as dark matter component, together with the characteristic features
of this scenario in the minimal Inverse Seesaw mechanism. The possibility of
successfully accounting for the baryon asymmetry in a testable realisation of
the leptogenesis mechanism is also addressed. On the other hand it is important
to look for manifestations of sterile fermions in laboratory experiments. We
address this point by making predictions for the expected rates of rare lepton
number violating decays of vector bosons, that can be mediated by sterile
fermions, as well as by studying the impact of sterile fermions on global fit
of electroweak precision data.
