LIQUID crystals were first discovered over 100 years ago in studies of cholesterol and related molecules. Liquid crystals are a fourth state of matter; they have greater ordering than more normal liquids but less ordering than crystalline solids. All phase changes have a characteristic phase transition temperature for a given set of conditions. Liquid crystals have separate transition temperatures where they change into "normal" liquids (melt) and into "normal" solids (solidify). Liquid crystals have become very common in the last 20 years as displays for electronic devices. This is the result of the unusual optical and electrical properties of liquid crystals. The long thin liquid crystal molecules cause light to travel at different speeds along the molecular axis and perpendicular to that axis. This leads to their ability to rotate the plane of polarized light.
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