The standard model (SM) of fundamental interactions, has been the
successful theory over the last 25 years.  The overall success of the SM in
describing the elementary interactions, the discovery of gauge bosons at
CERN in the eighties as well as the top discovery at Fermilab in 1995,
strengthened the expectation that the Higgs mechanism is the one that gives
mass to all particles.  At the moment the Higgs particle is the only missing
pieces of the puzzle.