Viruses that infect bacteria–known as bacteriophages–are the most abundant living things on Earth. (Yeah, that’s right. I called viruses living things. You gotta problem with that?) For nearly a century, doctors and scientists have dreamed of using them as medical weapons against the microbes that make us sick. Over at the University of Chicago Press’s blog, I discuss the enduring dream of phage therapy with MIT phage engineer Tim Lu, whom I profiled last year for Technology Review. This is my third UCP blog post to celebrate the publication of A Planet of Viruses; the next and last will appear next Friday.