  The observation of neutrino masses leads to the possibility of leptonic
mixing and CP violation. One of the simplest extensions of the Standard Model
giving rise to neutrino masses consists of the introduction of one righthanded
neutrino field per generation, singlet of SU(2). In the context of the seesaw
mechanism this leads to three light and three heavy neutrinos. The charged
current interactions couple the charged leptons to both the light and the heavy
physical neutrinos and leptonic CP violation may occur at low energies as well
as at high energies giving rise to the possibility of leptogenesis. There are
special scenarios where it is possible to establish a connection between CP
violation at the two different scales, an interesting example is included in
this work. Furthermore, we describe how the conjecture that all phenomena of CP
violation present in nature could have a common origin can be realized in the
framework of a further minimal extension of the Standard Model with CP broken
through the phase of the vacuum expectation value of a complex Higgs singlet.
