In 1946, while experimenting with how viruses infect common bacteria, Salvador E. Luria - then a professor at Indiana University - noticed a strange deviation from the usual pattern of events. Most viruses produce a new generation of themselves after infecting a bacterial cell; that's how they reproduce. But sometimes, this particular virus didn't. Why? What followed over the course of the next decade was an illustration of how discovery often depends on a chance observation falling on a receptive eye and how useful the principle of "controlled sloppiness" can be to a trained researcher, provided one is aware of the element of untidiness. Luria would eventually win the Nobel Prize for his research on bacteria, which all started with that one little mystery.