Until a decade ago, scientists were not aware that bacteria had complex immune systems – ones that could keep up with the pace of evolution in viruses called phages that infect bacteria. That changed with the discovery of what is now the most famous bacterial immune mechanism: CRISPR. Scientists realized that CRISPR is a natural gene editor, and it has revolutionized the world of biological research in thousands of labs around the world. Researchers now understand that most microorganisms have sophisticated immune systems of which CRISPR is just one element; but there has been no good way to identify these systems.