For over 100 years, Pablo Picasso's Woman Ironing has concealed another painting beneath its surface. Art historians have known this to be true since the late eighties, but thanks to infrared imaging the long-hidden work has now been unveiled. John K. Delaney, senior imaging scientist at the National Gallery of Art in Washington, used two types of infrared cameras, one hyper-spectral and one multi-spectral, to compose a highly-detailed image of the painting. In a New York Times article yesterday, the paper revealed the story behind the mysterious painting, and its website includes an interactive image that lets you "scratch" away the surface of Woman Ironing to reveal the image beneath. The painting is currently on show at New York's Guggenheim museum as part of its Picasso Black and White exhibition.