Kevin Esvelt knows the stakes are high. As a geneticist at the MIT Media Lab, Kevin discovered a technique called a gene drive, which gives humans a power we’ve never had before: to change the DNA of entire species in nature. Used successfully for good, a gene drive has the potential to save millions of lives by eliminating diseases like malaria. But in the wrong hands – or even in well-intentioned hands – the results could be catastrophic. How do we weigh the potential for enormous good against the terrifying unknowns?