Light is one of the most important and versatile phenomena in nature. Like a courier, it can transfer information from one point to another. Like an alchemist, it can alter matter. More specifically, it can initiate and moderate key processes in chemistry, biology and condensed matter. And of course, without it one could not see.

The versatility of light comes about because of the many forms it can take: brief flashes, focused spots, broad continuous beams, dim or intense light, polarized light, low- or high-frequency light, and light containing many frequencies at once. For visible light, the frequency determines the color and is related to the light's wavelength (shorter wavelengths correspond to higher frequencies). That most familiar of artificial light sources, an incandescent bulb, emits light across the full visible spectrum, resulting in white light.