Lattice defects of organic molecular crystals affect their optical or electrical properties by changing the local energy structure. Lattice defects also playa very important role in the chemical and physical properties, for example, as an active site of a catalyst or an initiating point of a solid state reaction. However, very little has been reported on the defect structure of real organic crystals. In the past ten years it became clear that the origin and the structure of the defects depend on the geometrical and chemical nature of the building units of the crystal, the molecules. Molecular...