Abstract We review basic physics of photonic crystals, discuss the relevant fabrication techniques, and summarize important device development in the past two decades. First, photonic band structures of photonic crystals and the origin of the photonic band gap are analyzed. Fundamental photonic crystal structures, such as surfaces, slabs, and engineered defects that include cavities and waveguides, are examined. Applications at visible and infrared wavelengths require photonic crystals to have submicron features, sometimes with precision down to the nanoscale. Common fabrication methods that have helped make such exquisite structures will be reviewed. Lastly, we give a concise account of key advances in photonic crystal-based lasers, light-emitting devices, modulators, optical filters, superprism-based demultiplexers and sensors, and negative index materials. Electron-beam nanolithography has enabled major research progress on photonic crystal devices in the last decade, leading to significant reduction of size and/or power dissipation in devices such as lasers and modulators. With deep ultraviolet (DUV) lithography, these devices may one day be manufactured with the prevalent CMOS technology at affordable cost.