Divergent beam images of colloidal crystals taken through an optical microscope. The threefold symmetry of a face-centered cubic crystal can be seen in the lower right image. In the other three images, the arrays of fine lines arise from Bragg rods related to the random hexagonal close-packed structure common to hard sphere colloids. When these rods are tilted with respect to the optical axis of the microscope, the images take on a "string art" appearance as seen in the upper right and lower left images, Images such as these can be used to extract crystallographic data from colloidal crystals. The arrows in the upper left image mark examples of Kossel pairs that are used for data extraction. For further details see the paper by Rogers and Lagerlöf, pp. 1867-1879.