The cycloaddition and -reversion of coumarin is one of the most prominent examples of reversible photo-driven reactions, which are used in a broad field of applications. By applying different illumination...

The use of light for shaping and changing matter is of high relevance in polymer and material science. Herein, a photopolymer method is presented, which comprises the combination of 3D photo‐printing at 405 nm light and subsequent modification under two‐photon absorption (TPA) conditions at 532 nm light, adding the fourth dimension. The TPA‐triggered cycloreversion reaction of an intramolecular coumarin dimer (ICD) structure occurs within the absorbing material. The 3D‐printable matrix does not show any degradation under the TPA conditions. With the presented photochemical tool of TPA processes inside absorbing 3D photo‐printable matrices, new possibilities for post‐printing modification, e. g. for smart materials, are added.