CRISPR, or clustered regularly interspaced short palindromic repeats, are an essential part of bacterial immunity designed to defend against foreign DNA. In bacteria, CRISPR acts just like it does in human cells as a pair of scissors, in their case with the goal of cutting strands of infecting DNA. While researchers have known that CRISPR is found in roughly half of all bacteria in the wild, they did not know much about the molecular battle between CRISPRs and invading viruses or phages.