  Topological interactions are an essential ingredient for building consistent
low-energy theories of fermions, gauge fields and Nambu-Goldstone bosons in the
absence of explicit UV completions, such as in Little Higgs models. These
interactions are also a probe of UV completion physics that may be out of
direct experimental reach. The technology of topological, or Wess-Zumino-Witten
interactions is described, using explicit examples in the standard model and in
Little Higgs models. The construction of a simple topological action on
SU(3)/SU(2) is described. Inconsistencies in some popular Little Higgs models
are pointed out.
