Photochromic molecules, or photochromes, can be reversibly isomerized between two thermally stable forms by exposure to light of different wavelengths. Upon isomerization, properties such as excitation energies, redox properties, charge distribution, and structure experience significant changes. These changes can be harnessed to switch “on” or “off” the action of a variety of photophysical processes in the photochromic constructs, e.g., energy and electron transfer. Until now, the focus of my research has been to show proof of principle for a large selection of molecule-based photonically controlled logic devices (solution based) with the functional basis in the switching of the transfer processes mentioned above. Now, I wish to extend the study to include experiments in the solid state, e.g., polymer matrices. Taking the step into doing solid state chemistry is not only a prerequisite for any real-world application. It will also allow for experiments that cannot be performed in fluid solution, such as aligning molecules in a stretched film for chemistry with polarized light, and immobilization of molecules for selective addressing in a three-dimensional array of volume elements. Furthermore, I intend to investigate the possibility to photonically control the membrane penetrating and the DNA-binding abilities of photochromes, aiming at, in a long-term perspective, light-activated cancer drugs. Due to the fact that both the structure and the charge distribution of a photochrome may change drastically upon isomerization, one of the two isomeric forms is often suitable for penetrating a membrane. Inside the membrane, e.g., in a cell, the photochrome can be photo-isomerized to a structure with high affinity for strong binding to DNA. Upon binding, transcription is inhibited and the cell dies. If desired, pH-sensitivity and two-photon processes could be used to further increase the selectivity in addressing very specific regions of the body, such as a tumor.