THE FIRST 3D PHOTONIC CRYSTAL operating at a wavelength of 1.5 microns, the all- important preferred wavelength for light traveling down optical fibers, has been devised by scientists at Sandia (Shawn Lin, slin@sandia.gov). Basically, a photonic crystal is to light what a semiconductor is to electrons: some photon energies are permitted while others are excluded. The exclusion comes about by a careful interleaving of materials with very different indices of refraction. The Sandia crystal is actually a tiny pile of criss-crossed polysilicon rods with air in between. Photonic crystals will be ingredients in future optical transistors---by deflecting light they will be able to act as optical switches at THz speeds; by trapping light they will be able to produce optical amplification within cavities. The crystals will also be part of other optical integrated circuit components such as low-power nanolasers and as waveguides. (Optics Letters, 1 Jan 1999; see also Physics Today, Jan 1999. Figure at Physics News Graphics.)