We explain how to construct a large class of new quiver gauge theories from branes at singularities by orientifolding and Higgsing old examples. The new models include the MSSM, decoupled from gravity, as well as some classic models of dynamical SUSY breaking. We also discuss topological criteria for unification.
"Geometry of particle physics." Adv. Theor. Math. Phys. 13 (4) 947 - 990, August 2009.