Liquid crystals are known for their fascinating optical properties. This work describes the experiments on light scattering and theoretical calculations on nonlinear optics in liquid crystals. Light scattering is a powerful tool to study the viscoelastic response of liquid crystals which is an essential parameter for display industry. Both thermotropic and lyotropic systems were probed by light scattering. Thermal nonlinearities in cholesteric liquid crystals are described in this book and various surprising liquid crystal phase transitions in the presence of a laser beam are reported. The work described in the book is based on Ph.D. work carried out by Amit K Agarwal at the Raman Research Institute, India and all intellectual and other legal rights arising out of this work are owned by the Institute and they are acknowledged and protected.