In a new study, scientists have transformed glass into a semiconductor that can harvest energy from light. The team uses near-infrared femtosecond laser pulses to rearrange the molecules in tellurite glass, forming trigonal tellurium nanocrystals with photoconductive properties and building new functionality into an existing material. "The intriguing facet here is the ability to add functionality into a material without adding any material," says Yves Bellouard, a microengineer and head of the Galatea lab at the Ecole Polytechnique Fédérale de Lausanne in Switzerland.