About the Cover:

Learning Crystallography Using Two-Dimensional Colloid Crystals. Under the right conditions, microscopic latex spheres readily form two-dimensional colloidal crystals. This month’s cover illustrates how the evaporation of solvent from a suspension of 2.13 μm latex spheres results in the formation of such crystals. The 28 still images, which start in the upper left corner and run from left to right, are from ~25 seconds of video taken using a compound optical microscope. The two-dimensional crystals formed by this process diffract visible light, thereby allowing their structures to be investigated using commonly available laser light sources. As described in the article by Bosse and Loening, students use these colloid crystals to learn the basic principles of crystallography in a hands-on fashion.