We discuss leptonic mixing and CP violation at low and high energies,
emphasizing possible connections between leptogenesis and CP violation at low
energies, in the context of lepton flavour models. Furthermore we analyse weak
basis invariants relevant for leptogenesis and for CP violation at low
energies. These invariants have the advantage of providing a simple test of the
CP properties of any lepton flavour model.Comment: 26 pages, no figures, submitted to the Focus Issue on `Neutrino
Physics` edited by F. Halzen, M. Lindner and A. Suzuki, to be published in
New Journal of Physic