Summary: The shapes of the spots observed on X-ray photographs of single crystals are influenced by the experimental method used, the properties of the incident beam, and the shape, absorption, structure, and texture of the crystal examined. If the first three factors can be allowed for, it is possible to obtain useful and interesting information concerning the sub-crystalline structure and the departures from regularity of the atomic or molecular arrangement. The limitations of the particular X-ray method used are illustrated by Laue and rotation photographs of a spirally distorted crystal of urea oxalate, and spiral and asterism effects in diamond and bröggerite photographs are also shown.