Thirty years ago, Dr. Arnold had an idea: to breed molecules in the laboratory the way we breed animals - to bring out the traits we want in them. The molecules she was particularly interested in were enzymes, which are essential to life, and which she knew could be used to make environmentally friendly materials, including bio-fuels, cleaning products, and pharmaceuticals. Her idea worked right away. It’s now called “directed evolution,” and it has had huge implications for industry. In 2018, it earned her a Nobel Prize in Chemistry (only the fifth ever awarded to a woman). She talks here about the science, but also about the bumps in her life that helped her become an original thinker.