One of the most significant revolutions in science is underway, and yet most people haven't even heard of it. It's called CRISPR, and it is an easy, inexpensive process for cutting and pasting DNA - the code of life. It is already being used in human trials to cure genetic disease, and it promises to transform agriculture, with drought-resistant crops that will better feed the world. But it also threatens to usher in a frightening era of designer babies and unintended consequences. The two lead scientists behind CRISPR, Jennifer Doudna and Feng Zhang, talk here about their lives and their research, and they sound the alarm about the dangers of their own discovery.