Studying galactic interactions is like sifting through the forensic evidence at a crime scene. Astronomers wade through the debris of a violent encounter, collecting clues so that they can reconstruct the celestial crime to determine when it happened. Take the case of M82, a small, nearby galaxy that long ago bumped into its larger neighbor, M81. When did this violent encounter occur? New infrared and visible-light pictures from the Hubble telescope reveal for the first time important details of large clusters of stars, which arose from the interaction.