An intense x-ray beam has finally revealed a hidden portrait in one of Edgar Degas’s paintings, The New York Times reports. Portrait of a Woman, painted around 1880, was long suspected to have another image looming just beneath the surface. As the oil paint thinned with age, a dark stain on the subject’s face slowly became more prominent. Conventional x-rays revealed the shadowy outline of another woman hidden beneath, but not much else. Now, in a study published in Scientific Reports, researchers used a particle accelerator to reveal a portrait of one of Degas’s favorite models, Emma Dobigny, that he covered up later with a different painting. This new technique—which provides a new way of examining artwork without risking destruction—can not only provide insight into Degas’s painting techniques, but also help identify forgeries.