As with many new fields, synthetic biology—which incorporates disparate disciplines like engineering, computer science, biotechnology, and molecular biology—is hard to pin down. But a rough working definition says that it is the application of the principles of engineering to biological systems. Instead of using engineering’s discrete modules of code, transistors, resistors, and capacitors, synthetic biology builds things from sequences of genetic material. The field has remarkable potential and has already been used to aid the production of antimalarial drugs and synthetic flavorings. One researcher used mail-order DNA and a genetic map available online for free to create a live polio virus. The implications could be enormous.