Abstract Molecular architectures containing photosensitive units respond to light, giving dramatic variations of their structure. In particular, the crystalline packing phases offer the possibility of significant advances in crystal design and the understanding of solid-state photoreactivity. In this review we mainly focus on three different photoreactivity patterns, namely the isomerization of azobenzene, open-ring↔closed-ring transformations of diarylethenes and cycloadditions of olefin pairs, as well as some examples of photoreactive crystals outside these types. Many interesting phototriggered functionalities are documented herein, such as photo-tuning of guest adsorption of azobenzene or diarylethene-based porous frameworks and crystalline organic polymers generated by photo-cycloaddition reactions taking place in the different networks.