Prokaryotes have long been at war with bacteriophage. The evolutionary pressure of this struggle has led both sides to develop sophisticated defenses. Notably, CRISPR-Cas systems evolved to let bacteria and archaea record past infections and rapidly squelch subsequent viral invasions. First, CRISPR proteins capture nucleic acids to build a genomic gallery of "molecular mugshots." Next, the mugshots are printed into RNA copies and distributed amongst CRISPR interference proteins. These RNA-guided bounty hunters precisely identify and cleave offending genomes to halt infection. No system is fool-proof, however, and recent work has elucidated an impressive arsenal of "anti-CRISPR" proteins that bacteriophage deploy to evade destruction. Studying this on-going arms race has yielded a treasure trove of biotechnology tools. I will discuss the stages of CRISPR immunity while highlighting how scientists have co-opted its various proteins for diverse applications.