Liquid Crystals that exhibit a phase of matter that has properties between those of a conventional liquid and those of a solid crystal. For instance, a liquid crystal (LC) may flow like a liquid, but have the molecules in the liquid arranged and or oriented in a crystal-like way. These are the substances having a state of aggregation intermediate to highly ordered solid and disordered liquid. That is intermediate state between solid and isotropic liquid. These intermediate phases are called “Liquid Crystal Phase or Mesophase”; meso means in between (the crystal and the liquid phase).Liquid crystals may also be called crystalline liquids.

In 1888, the Austrian botanical physiologist Friedrich Reinitzer (1858-1927), (interested in the biological function of cholesterol in plants) was looking at the melting behavior of an organic substance related to cholesterol (cholesteryl benzoate and cholesteryl acetate).

liquid-crystalline esters

He found out that cholesterol benzoate does not melt like other compounds but obviously had two melting points. At 145.5°C, it melted into a cloudy liquid and at 178.5°C, it melted again and cloudy liquid suddenly became clear. Furthermore, the phenomenon was reversible. Discussion with Otto Lehmann and others led to the identification of a new phase of matter called the liquid crystal phase.