  The Standard Model (SM) of particle physics was finalized in its current form
in the mid-1970s, and has been extensively tested and confirmed ever since,
with the discovery of the Higgs boson in 2012 being the last missing piece.
While no new particles have been directly discovered at the Large Hadron
Collider (LHC) at CERN so far, precision observables sensitive to quantum
effects of new particles have accumulated intriguing hints for physics beyond
the SM. All these anomalies can be interpreted from the point of view of lepton
flavor universality, i.e., as hints that electrons, muons, and tau leptons
differ much more than predicted by the SM. These tensions can be explained by
postulating the existence of new exotic particles. Future measurements will be
able to conclusively test this hypothesis, potentially providing long-awaited
evidence how the SM needs to be extended at high energies.
