Stimuli responsive materials that are able to twist, bend, deform, move or change their shape can find multiple applications in manufacturing of smart devices and/or medicine. Spin-crossover materials are sensitive to light, temperature or pressure changes. Here we propose a comprehensive X-ray diffraction study of pressure-, temperature- and light-switchable materials. In order to better understand the underlying mechanisms of pressure-induced structural transformations and spin-crossover transitions, we propose to perform a series of comprehensive high-pressure (0.1MPa - 10GPa) single crystal diffraction measurements for 1D, 2D and 3D iron(II) coordination polymers.