Over the past 25 years or so there has been a revolution in the devel- mentoffunctionalpolymers. Whilemanypolymersascommoditiesrepresent huge markets, new materials with a high degree of functionality have been developed. Such specialty polymers play important roles in our day-to-day lives. The current volumes 213 and 214 of Advances in Polymer Science focus on photoresponsive polymers. In particular polymers that can either change the properties of a beam of light that passes through them or who change their properties in response to light. Volume 213 starts with an introd- tion to two-photon absorption by Rumi, Barlow, Wang, Perry, and Marder. In this chapter they develop the basic concepts of two-photon absorption, and describe structure-property relationships for a variety of symmetrical and unsymmetrical molecules. The applications of these materials in 3D - crofabrication of polymers, metals, and oxide materials are detailed in the chapterentitled Two-PhotonAbsorberandTwo-PhotonInduced Chemistry contributed by the same group of authors. Then Bel?eld, Bondar, and Yao describe the molecules, dendrimers, oligomers, and polymers that can be - cited by two-photonabsorption and their application in processing materials with three-dimensional spatial control in their chapter entitled Two-Photon Absorbing Photonic Materials.

Speci?cally they describe the development of symmetrical and polar conjugated materials for two-photon absorption and their use as photo-initiatorsfor3D microfabrication. Juodkazis,Mizeikis, and Misawaalsoexploremultiphotonprocessingofmaterials intheirchapter,and provide more focus on the processing aspects of these materials and discuss thestate-of-the-artinresolution.