In normal crystalline solids the atoms are located in fixed locations. In normal liquids, the molecules are free to move about randomly. There are no three-dimensional fixed positions of the moelcules.
Liquid crystals are states of matter intermediate between normal crystals and normal liquids.
The first liquid crystal that was discovered was an organic material related to cholesterol called cholesterol benzoate. It was discovered by an Austrian botanist, Friedrich Reinitfer in 1888. The crystals selectively reflect light of wavelengths equal to the helix pitch length, so that a color will be reflected when the pitch is equal to the corresponding wavelength of light in the visible spectrum. As the temperature of the crystal increases so does the pitch of the helix and so does its color. They have applications in medicine, electronics, aero space and many other areas.