To help detect infectious diseases such as anthrax, HIV, and smallpox, researchers from Northwestern University developed a technique for creating DNA detection probes to "fingerprint" these biological agents. Attached to tiny gold particles are molecules that provide a unique signal (the "fingerprint") when a light is shined on them and a single strand of DNA designed to recognize and bind a target of interest. If a disease target is present in the sample being tested, strands of DNA bind to the appropriate spot on the chip. Corresponding nanoparticle probes latch onto any matches, which are then coated with silver. A laser scans the chip, and signals for the probes are recorded. A unique "fingerprint" can be designed for each biological agent. For more information, contact Chad Mirkin at firstname.lastname@example.org.