Technologies for directing light on a microscopic scale. This area of photonics has had a major impact on telecommunications. In order to keep up with the Internet's exploding need for bandwidth, technologists are looking to replace electronic switches with faster, smaller optical devices. Enter the photonic crystal: a few ultrathin layers of nonconducting material that reflect various wavelengths of light. Photonic crystal may provide the means to create optical circuits (and other small, inexpensive, handheld devices) that can carry, direct, and process data quite literally at the speed of light. It is said that photonic crystals are to photons what semiconductors are to electrons.