The Austrian botanist Friedrich Reinitzer, who studied the function of cholesterol in plants, discovered in 1888 that a cholesterol benzoate crystal, when heated, does not melt like an ordinary crystal but turns at 145°C into a milky liquid, which becomes perfectly clear at 178.5°C. Convinced that he had discovered a new state of matter, he sent it to Otto Lehman, who became famous for using the polarized light microscope in crystallography. Lehman had built a heating plate that allowed him to visualize the evolution of a crystal when it was heated, and he interpreted this milky state as an ordinary crystalline phase with a highly mobile three-dimensional lattice. He then extended Reinitzer’s discovery to a large number of natural and artificial substances and, to recall these apparently contradictory characteristics, gave them the name “Liquid Crystal” in 1904. Reinitzer also showed that these liquid crystals have the property of rotating the polarization direction of light (Figure 5.1). Between cross-polarizers, a liquid sample appears black and a liquid crystal bright. https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429154355/75121c3f-9fce-4f28-b106-96ade177249e/content/fig5_1_PB.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429154355/75121c3f-9fce-4f28-b106-96ade177249e/content/fig5_1_OB.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/>