When a curator at Yale University started digging through his gallery’s storage space, he wasn’t expecting to find anything special. But within the piles of mediocre works, a 1.5-meter-tall canvas caught his eye. Called The Education of the Virgin, it depicted a very young Virgin Mary being taught to read by her parents, St. Anne and St. Joaquim. Its surface was badly damaged, with cracked paint and parts of the image worn away. Even still, the curator thought he recognized the hand behind the painting: The 17th century Spanish master Diego Velázquez. But how to know for sure?