A key advantage of polymeric materials over more conventional optical materials such as glass, is the considerably larger variation that their refractive index undergoes with temperature. The large magnitude of the thermo-optic coefficient dn/dT (about 25 times larger in most polymers than in glass) can be leveraged to produce power-efficient thermally actuated dynamic photonic components. We review the global advances in thermo-optic polymeric components which include switches, tunable filters, and variable optical attenuators (VOA's). NxN switches can be digital optical switches based on X junctions or Y junctions, or they can be interferometric switches based on directional couplers or Mach-Zehnder interferometers (MZI's), including generalized MZI's (GMZI's) which are compact devices that consist of a pair of cascaded NxN multimode interference (MMI) couplers with thermal phase shifters on the N connecting arms; tunable filters can be based on phasars, gratings, thin films, or microring resonators; and VOA's can be based on interferometry, mode confinement, or switching principles.