The micrograph is of a mixture of CB8CB (10 wt%) and HNG-7156 in a 10-micron vertical alignment cell at room temperature, viewed between crossed-polarizers. This comes from a study we performed, varying the length of the carbon chain linker of the dimeric mesogen in the mixture. All of the mixtures with odd number spacers (for example, CB7CB) in VA cells formed a homogeneous nematic phase and appeared completely dark under POM. However, CB8CB crystallizes at room temperature, creating patterns such as those seen in the image. Presumably, this is yet another example of the "odd-even" effect in action.