CP violation in B and K meson decays is not surprisingly one of the central topics in particle physics. Indeed, CP-violating and rare decays of K and B mesons are very sensitive to the flavour structure of the Standard Model (SM) and its extensions. In this context a very important role is played by the Cabibbo-Kobayashi-Maskawa (CKM) matrix [1,2] that parametrizes the weak charged current interactions of quarks: its departure from the unit matrix is the origin of all flavour violating and CP-violating transitions in the SM and its simplest extensions.