Synthetic biology is the technique that enables us not just to read and edit but also write DNA to program living biological structures as though they were tiny computers. Unlike cloning Dolly the sheep-which cut and copied existing genetic material-the future of synthetic biology might be something like an app store, where you could download and add new capabilities into any cell, microbe, plant, or animal. This breakthrough science has the potential to mitigate, perhaps solve, humanity's immediate and longer-term existential challenges: climate change; the feeding, clothing, housing, and...