Liquid Crystals offers readers a concise yet comprehensive introduction to the basic principles underlying the unique physical and optical properties of liquid crystals. Written by an internationally recognized pioneer in the field of nonlinear optics specializing in the nonlinear optics of liquid crystals, it also affords readers a rare opportunity to benefit from a leading expert's considerable professional insights into the mechanisms and theoretical principles behind nonlinear optical phenomena occurring in liquid crystals. The first part of Liquid Crystals is devoted to the physical properties of the thermotropic liquid crystals. Following a discussion of their molecular and chemical structures, the author delves into all major theoretical aspects of their isotropic and liquid crystalline phases. Receiving special attention are physical parameters such as order parameters, elastic constant, Free energy, viscosity and flows, refractive indices, and birefringence. Relatively new materials such as polymeric liquid crystals, polymer dispersed liquid crystals, dye-doped liquid crystals, and ferroelectric liquid crystals are explored in detail, as are light scatterings, including Raman, Brillouin, Rayleigh, and Rayleigh Wing scatterings. The second part of Liquid Crystals is concerned with nonlinear optical phenomena - especially nonlinear optical responses of liquid crystals to light and laser fields. In this section, Professor Khoo explores all the known mechanisms for optical nonlinearities in the principal mesophases of liquid crystals; introduces the basic principles, phenomena, and terminology in nonlinear optics; and provides a comprehensive summary of the major nonlinear optical phenomena observed in liquid crystals to date. The first concise yet all-inclusive introduction to the subject, Liquid Crystals functions equally well as an upper-level student text for optical engineering courses and a basic reference for researchers in optical engineering.