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Liquid crystal
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<p>Liquid crystal (LC) is a <a href="/facts/State_of_matter/ojlIA1UF">state of matter</a> whose properties are between those of conventional <a href="/facts/Liquid/t9GkLWzt">liquids</a> and those of solid <a href="/facts/Crystal/e2R2mk3E">crystals</a>. For example, a liquid crystal can flow like a liquid, but its <a href="/facts/Molecules/N9ljSfFq">molecules</a> may be oriented in a common direction as in a solid. There are many types of LC <a href="/facts/Phase_(matter)/NkHXDdN3">phases</a>, which can be distinguished by their <a href="/facts/Optics/p0vq4S1T">optical</a> properties (such as <a href="/facts/Texture_(crystalline)/c4rhvqus">textures</a>). The contrasting textures arise due to molecules within one area of material ("domain") being oriented in the same direction but different areas having different orientations. An LC material may not always be in an LC state of matter (just as water may be ice or water vapour). </p><p>Liquid crystals can be divided into three main types: <a href="/facts/Thermotropic/u1nY7pda">thermotropic</a>, <a href="/facts/Lyotropic/4deMh9Uq">lyotropic</a>, and metallotropic. Thermotropic and lyotropic liquid crystals consist mostly of <a href="/facts/Organic_molecules/gqCNaN45">organic molecules</a>, although a few minerals are also known. Thermotropic LCs exhibit a <a href="/facts/Phase_transition/eLP2BY8R">phase transition</a> into the LC phase as temperature changes. Lyotropic LCs exhibit phase transitions as a function of both temperature and <a href="/facts/Concentration/wqBmz5od">concentration</a> of molecules in a <a href="/facts/Solvent/LoMPMz8S">solvent</a> (typically water). Metallotropic LCs are composed of both organic and inorganic molecules; their LC transition additionally depends on the inorganic-organic composition ratio. </p><p>Examples of LCs exist both in the natural world and in technological applications. Lyotropic LCs abound in living systems; many proteins and cell membranes are LCs, as well as the <a href="/facts/Tobacco_mosaic_virus/36sVcLw2">tobacco mosaic virus</a>. LCs in the mineral world include solutions of <a href="/facts/Soap/S3nJa1oY">soap</a> and various related <a href="/facts/Detergent/4FLKXR6p">detergents</a>, and some <a href="/facts/Clay/xnwouEkB">clays</a>. Widespread <a href="/facts/Liquid-crystal_display/8B6xGBEz">liquid-crystal displays</a> (LCD) use liquid crystals. </p>