  Matter-Higgs unification in string-inspired supersymmetric Grand Unified
Theories predicts the existence of colored states in the Higgs multiplets and
calls for two extra generations of Higgs-like fields ('unhiggses'). If these
states are present near the TeV scale, gauge-coupling unification points to the
existence of two distinct scales, 10^15 GeV where right-handed neutrinos and a
Pati-Salam symmetry appear, and 10^18 GeV where complete unification is
achieved. Baryon-number conservation, while not guaranteed, can naturally
emerge from an underlying flavor symmetry. Collider signatures and dark-matter
physics may be drastically different from the conventional MSSM.
