Optical or magnetic characteristics can change upon decrease of particle sizes to very small dimensions (around 100 nm or well below, depending on the requested effect), which is in general of major interest in the area of composite materials. With this respect, frequently considered features are superparamangetism or optical properties (for example, the extent of light scattering or, in the case of metal particles, the color). The reduction in light scattering upon usage of nanoparticles can also be of interest in combination with other properties which favorably improve characteristics of polymeric materials, such as UV absorption, photoconductivity or modification of refractive indices. Certain optical effects, for instance iridescence or dichroism, emerge only by particular distributions of the nanoparticles within the polymer matrix. The fact that properties of nanocomposites can differ from those of analogous composites with larger particles self-evidently offers a plethora of opportunities for the creation of materials with exceeding performance.