Having a fast and easy way to cut out and replace genes could revolutionise areas of biology as diverse as medicine and agriculture. And the discovery of the gene editing tool using CRISPR-cas9 makes that revolution a present reality. But the teams that revealed this gene editing tool piece by piece were not looking for anything to do with genetic engineering: instead they were curious to know more about how bacterial immunity works. Presenter Adam Hart speaks with Professor Jennifer Doudna of the University of California, Berkeley, and Dr Rodolphe Barrangou of North Carolina State University to reveal the story of how scientific curiosity can accidentally change the world. Produced by Rory Galloway. First broadcast on Friday 27 July 2018.