The physical phenomenon of spin-crossover in molecular crystals is a multiscale process whose properties rely on the supramolecular organization of the spin-crossover active elements, their interactions within the crystal packing, and their dynamics. The delicate balance between short-range and long-range structural reorganizations upon the spin transition is at the origin of remarkable and fascinating physical phenomena such as thermal, light-induced and pressure-induced hysteresis, multi-step transitions, or multimetastablility. A complete understanding of the various phenomena associated with spin-crossover requires a comprehensive and thorough characterization of the overall structural architecture at all scales, which goes beyond the average static crystal structure. This Tutorial surveys the practical use of x-ray crystallography notably in non-ambient conditions to provide a direct view of the physical processes operating in spin-crossover molecular solids from bulk single crystals to nanocrystalline powder. Advanced x-ray crystallography methods are reviewed and illustrated with a series of model examples.