This chapter reviews recent piezo- and photo-crystallographic approaches to spin-crossover (SCO) materials highlighting the role of structural features in the SCO process. The SCO phenomenon is highly pressure-sensitive. The chapter emphasizes the need for crystallography under high pressure, that is piezo-crystallography, in the field of SCO. It illustrates that photo-crystallography experiments are not merely data collections under laser irradiation. Accordingly, it is shown that through varying different external parameters (such as temperature, laser irradiation wavelength or power) and careful investigation of the structural signatures, key information on the different processes can be obtained. For instance, it has been observed that for some systems the nature of photoinduced state can be triggered by choosing appropriate excitation wavelength.