  The Large Electron Positron Collider (LEP) established the Standard Model
(SM) of particle physics with unprecedented precision, including all its
radiative corrections. These led to predictions for the masses of the top quark
and Higgs boson, which were beautifully confirmed later on. After these
precision measurements the Nobel Prize in Physics was awarded in 1999 jointly
to 't Hooft and Veltman "for elucidating the quantum structure of electroweak
interactions in physics".
  Another hallmark of the LEP results were the precise measurements of the
gauge coupling constants, which excluded unification of the forces within the
SM, but allowed unification within the supersymmetric extension of the SM. This
increased the interest in Supersymmetry (SUSY) and Grand Unified Theories,
especially since the SM has no candidate for the elusive dark matter, while
Supersymmetry provides an excellent candidate for dark matter. In addition,
Supersymmetry removes the quadratic divergencies of the SM and {\it predicts}
the Higgs mechanism from radiative electroweak symmetry breaking with a SM-like
Higgs boson having a mass below 130 GeV in agreement with the Higgs boson
discovery at the LHC. However, the predicted SUSY particles have not been found
either because they are too heavy for the present LHC energy and luminosity or
Nature has found alternative ways to circumvent the shortcomings of the SM.
