The book is devoted to a theoretical and experimental study of new nanostructural composite materials with quasi-zero refractive index. Such materials with silver nanoparticles in a dielectric matrix are synthesized in our scientific group and by way of pneumatic drawing layers from these materials on various surfaces was obtained.The speciments allowing to observe experimentally such optical phenomena as light interference in thick layers, the enhanced optical transmission, focusing of light in a composite layer, a broadband optical antireflection in the spectrum from 400 to 1200 nanometers are received. Theoretical approach for the description of optical properties of composite layers of various thickness on various surfaces at various incidence angles of light is presented. It is shown that the refractive index of layers in the interfal of quasi-zero values is represented as a continuous random variable. As shown in this book, these materials can find broad application, for example, in optical instrument making, in solar industry, in the masking of bodies(invisible cloaking problem) in visible spectrum, etc.