Chemical biologist Benjamin Cravatt is developing tools to illuminate the roles of proteins and enzymes in humans and animals. Cravatt and colleagues have synthesized dozens of fluorescent probes that chemically bind to enzymes in laboratory samples of healthy and diseased tissues, then light up when excited by a laser scanner. The technique can show which enzymes are more or less active in cancerous cells, which could herald a breakthrough for proteomics—the attempt to identify the structures and functions of human proteins. Cravatt’s protein-activity- based approach represents an advance over methods that merely infer protein function by comparing the abundance of proteins in samples. His technology also forms the basis of ActivX Biosciences in La Jolla, CA, which he cofounded in 2000 and now employs more than 40 people. Applications for the chemical probes include improving medical diagnostics, identifying new drug targets and facilitating drug tests. “Helping with the development of a single drug would be huge, ”the hyperkinetic researcher says, “but we hope to do this many times over.”