Seven years ago, an understanding of nature inspired a revolutionary new technology, when researchers turned a defense system used by bacteria to thwart viruses into the gene-editing tool now known as CRISPR. But for another emerging gene editor the understanding has lagged the applications. For several years, researchers have been adapting retrons—mysterious complexes of DNA, RNA, and protein found in some bacteria—into a potentially powerful way to alter genomes of single cell organisms. Now, biology is catching up, as two groups report evidence that, like CRISPR, retrons are part of the bacterial immune arsenal, protecting the microbes from viruses called phages.