Thomas Gaffield (1825-1900) investigated the patterns on the wings of the butterflies (notice the bodies are missing). He was well aware that various chemical compositions in manufactured glass caused changed color overtime and suggested certain kinds of glass for the skylights in photography studios. Courtesy of Smithsonian National Museum of American History hide caption

itoggle caption Courtesy of Smithsonian National Museum of American History

Alfred Stieglitz attached this photograph to a letter for Georgia O'Keeffe, dated July 10, 1929. Below the photograph he wrote, "I have destroyed 300 prints to-day. And much more literature. I haven't the heart to destroy this..." Yale Collection of American Literature, Beinecke Rare Book and Manuscript Library hide caption

itoggle caption Yale Collection of American Literature, Beinecke Rare Book and Manuscript Library

Baghdad's traffic, choked by hundreds of checkpoints, slows to a crawl while security forces inspect vehicles for weapons and explosives. Lynsey Addario/National Geographic hide caption

itoggle caption Lynsey Addario/National Geographic