Liquid crystal

Liquid crystals are a class of molecules that, under some conditions inhabit a phase in which they exhibit isotropic, fluid-like behavior--that is, with little long-range ordering--but which under other conditions inhabit one or more phases with significant anisotropic structure and long-range ordering.

Liquid crystals find wide use in liquid crystal displays, which rely on the optical properties of certain liquid crystalline molecules in the presence or absence of an electric field. In the absence of an electric field, these molecules remain isotropically disordered in solution, which remains transparent. In the presence of an applied electric field, these molecules align in such a way as to become opaque.

The ordering of liquid crystalline phases is extensive on the molecular scale, but does not extend to the macroscope scale as might be found in classical crystalline solids. The ordering in a liquid crystal might extend along one dimension, but along another dimension, might have significant disorder.