In the same way that barcodes on your groceries help stores know what’s in your cart, DNA barcodes help biologists attach genetic labels to biological molecules to do their own tracking during research, including of how a cancerous tumor evolves, how organs develop or which drug candidates actually work. Unfortunately with current methods, many DNA barcodes have a reliability problem much worse than your corner grocer’s. They contain errors about 10 percent of the time, making interpreting data tricky and limiting the kinds of experiments that can be reliably done.