Liquid crystals which possess orientational ordering but no positional ordering come in several different forms, most of which have been discovered only in recent years. These include some rather exotic structures, such as the cubic lattice blue phases and the amorphous fog phase found in cholesterics of high optical activity, and the biaxial nematic first discovered in a certain soap solution. It presents a series of optical experiments designed to probe the phase transitions of these materials. Their goal is to contribute to a better understanding of the many varieties of critical phenomena exhibited by systems, such as these, having tensor order parameters.
