  The Standard Model (SM) of particle physics represents our most fundamental
knowledge of elementary particles and their interactions. One of the cardinal
properties of the SM which has been thoroughly studied during the past years is
the so-called Lepton Flavour Universality (LFU): W and Z bosons are predicted
to be equally coupled to the three lepton generations. Hints for deviations
from LFU have been found by the LHCb collaboration in $b\to s\ell\ell$ and
$b\to c\ell\nu$ decays, sparking great interest and further motivating the
searches for lepton flavour violating processes. A general review of these
results is presented, including prospects in view of the LHC and LHCb upgrade.
