The formation of regular nanostructures by photolysis of chemically reactive crystals is investigated by atomic force microscopy (AFM) in relation to known crystal structures where available and with respect to different crystal faces. Thus, upon photodimerization of 2,5-dibenzylidenecyclopentanone 1 three products form stereoselectively though with far-reaching molecular transports along gliding planes giving both nanostructured trenches and volcanoes. [4+4]-Photodimerization of 9-chloroanthracene 5 provides exceptionally regular and stable flees and volcanoes on different faces, respectively, indicating the influence of bulk crystal structure to the formation of the nanostructures. The photoelimination of nitrogen from crystalline 3,6-diphenyltetrazine 7 yields nanostructures in the form of very regularly shaped craters, even though the product benzonitrile is a liquid.