While on a research trip in Peru, science journalist Alice Robb became hooked on lucid dreaming—the uncanny phenomenon in which a sleeping person can realize that they’re dreaming and even control the dreamed experience. Finding these forays both puzzling and exhilarating, Robb dug deeper into the science of dreams at an extremely opportune moment: just as researchers began to understand why dreams exist. They aren’t just random events; they have clear purposes. They help us learn and even overcome psychic trauma.