  The fundamental Higgs doublet may be replaced in the Standard Model by
certain non-perturbative four-quark interactions, whose effect is to induce a
composite Higgs sector responsible for electroweak symmetry breaking. A simple
composite two-Higgs-doublet model is presented. The four-quark interactions
arise naturally if there are either extra spatial dimensions or larger gauge
symmetries at a multi-TeV scale. Some theoretical and phenomenological
implications of these scenarios are discussed.
