Interest in nonlinear optics has been growing rapidly. Today many materials are known to possess nonlinear effects and the intense search for even more efficient and cost-effective materials is continuing. Various crystals are known for large nonlinear coefficients however their limitations in size and high cost make other solid state materials such as glass more attractive despite their relatively smaller non-linear coefficients. We review the research on glasses with high nonlinearity by classifying them into homogenous type and heterogeneous type. 1.