Nanomaterials exhibit dynamic optical properties that can be significantly different from bulk materials, such as absorption, transmission, and reflection. By altering their shape, size, and surface properties, numerous optical effects can be created. In some cases, nanofillers work in unison with conventional fillers to significantly enhance or modify the various properties of the materials into which they are integrated, such as the optical, electrical, mechanical, thermal, or fire-retardant capabilities. The fact that the optical characteristics of nanomaterials depend on their intrinsic electrical structure provides a thorough comprehension of their structure. Molecular orbitals of small nanoclusters have the most profound effect on energy when the dimensionality is reduced since the lowermost vacant orbital is the conduction band in essence and the uppermost occupied orbital is the valence band. Nanomaterial’s color is a result of the surface plasmon resonance effect, which happens when the surface electron band of the nanomaterial resonates with light wavelengths. Significantly, nanomaterials exhibit a variety of optical properties, which can be determined by spectroscopic methods. Reduction in the dimensionality of the electronic structure affects both the energy of the highest and lowest occupied molecular orbitals. The reduced dimensionality of nanomaterials also affects their abilities for photocatalysis, photoconductivity, photoemission, electroluminescence, and other properties. The current chapter explores the various characteristics of nanomaterials and provides a brief description of the optical characteristics of nanofillers.