What did the past smell like? A European team of historians and chemists is seeking to reproduce lost scents dating back as far as the 16th century. The Odeuropa project uses artificial intelligence to analyze references to smells in thousands of old images and texts. Once catalogued, researchers plan to re-create roughly 120 scents with the hope that museums use them to make exhibits more immersive—and ultimately so scientists can produce an encyclopedia of historical smells. Some of the scents might be pleasant, like the old-books aroma in the library at St. Paul’s Cathedral in London, while others, like the sewage that plagued some European cities, might be gross. But according to the team, past scents provide unique insight into our ancestors’ lives. As Cecilia Bembibre, a researcher at University College London’s Institute for Sustainable Heritage, told Discover magazine: “The way we interpret smells changes constantly with the cultural background and the moment we live in.”