Leptogenesis with Majorana neutrinos

I review the generation of a lepton asymmetry which is converted to a baryon excess at the electroweak phase transition. This scenario becomes very attractive if we can relate it to other physical phenomena. For this reason I elaborate on the conditions of the early universe which lead to a sizable lepton asymmetry. Then I describe methods and models which relate the low energy parameters of neutrinos to the high energy (cosmological) CP-violation and to neutrinoless double beta-decay.