Ever since the first barcode appeared on a pack of chewing gum in 1974, the now-ubiquitous system has enabled manufacturers, retailers and consumers to quickly and effectively identify, characterize, locate and track products and materials. In a paper first posted in the journal Cell, researchers at Johns Hopkins Medicine and The Johns Hopkins University demonstrate how they can do the same thing at the molecular level, studying the ways cancer cells “talk” with one another using a different kind of barcode system — one made up of combinations of patterns and colors, with each set tied to a specific biochemical activity in the communication network.