A number of tools used to explore the world of nanoscience and nanotechnology rely on probing the properties of matter with electromagnetic radiation, or light, at various wavelengths. The use of absorption or emission of light is generically known as spectroscopy. Depending on the wavelength, or the energy of the radiation, the light will probe different properties of the molecules or the material of interest. Table 14.1 provides an overview of the relationship between the wavelength, frequency, and the energy of the electromagnetic radiation and the corresponding energy transitions.