Researchers at the University of Illinois Urbana-Champaign, have demonstrated the first optoelectronically active 3-D photonic crystal. Uniquely, the material can both produce light from electricity (being electrically active) and direct light (being optically active). The researchers started with a template of closely packed spheres. Then they deposited gallium arsenide (GaAs) through the template, filling in the gaps. Once the template was full, the researchers removed the spheres, leaving a complex, porous 3-D structure of single-crystal semiconductor. They built a 3-D photonic crystal LED to test their fabrication method.