Detecting anthrax and other bioweapons typically requires bulky equipment. Now engineers at the University of California, Berkeley, and Purdue University have devised a sensor chip only five millimeters square that could do the job. The chip uses standard fluorescence detection technology but shrinks it enough that it can fit in a handheld device. A dye attached to a molecule that reacts with anthrax would be added to a test sample in a plastic cassette clipped to the chip. Light from a tiny light-emitting diode would make any sample containing anthrax glow, and a detector would pick up the fluorescence. The team is now looking for a partner to develop the chip into a product.