Tucked away among the letters, diaries, and other ephemera in the Smithsonian's archives lies a trove of rarely seen snapshots of some of the twentieth century's most celebrated artists. Unlike the familiar official portraits and genius-at-work shots, these humble snaps capture creative giants with their guard down, in the moment, living life. Pablo Picasso stands proudly on a balcony with young daughter Maya--a tiny, meticulously inked annotation...