Following over 120 years of research in liquid crystals, a large number of liquid crystal phases have been discovered. Their appearance depends on various criteria – their molecular structure and temperature, for example, as well as their concentration and the solvent.
The diagram shows the classification of liquid crystal phases.
Friedrich Reinitzer observed the phenomenon of liquid crystal phases in 1888 using the benzoate of cholesterol. He discovered a thermotropic liquid crystal. Soaps or tensides, for example, can form lyotropic phases which can consist of micelles or double layers.