The war between viruses and bacteria has been waged for over a billion years. Viruses called bacteriophages (or simply phages) require a bacterial host to propagate, and so they must somehow infiltrate the bacterium; such deception can only be achieved if the phage understands the genetic framework underlying the bacterium’s cellular functions. The phage’s goal is to insert DNA that will be replicated within the bacterium and lead to the reproduction of as many copies of the phage as possible, which sometimes also involves the bacterium’s demise.