"How do you explain to a 2-year-old or 4-year-old there's nothing to eat?" asks Kathy, a homeless mother. Michael Nye hide caption

itoggle caption Michael Nye

This Ansel Adams photograph of Acoma Pueblo, N.M., is among those now on display, decades after being commissioned. Ansel Adams/National Archives hide caption

itoggle caption Ansel Adams/National Archives

The cover of Sw!pe Volume 1. Cover art by Jack Laughner, type and design by Christopher D. Boynton Sw!pe/Red Hook Editions hide caption

itoggle caption Sw!pe/Red Hook Editions

Staff Sgt. Norman T. Hatch was a cinematographer and combat photographer during World War II. He won an Academy Award for his footage of the amphibious assault at the Battle of Tarawa in 1943. U.S. Marine Corps Combat Correspondents Association hide caption

itoggle caption U.S. Marine Corps Combat Correspondents Association

Dr. Martin Luther King Jr. is sprawled across a police desk as his wife looks on. He was arrested while trying to attend a hearing for civil rights leader Ralph Abernathy and was released when his identity became known to the police. Montgomery, Ala., 1958 Charles Moore/Black Star hide caption

itoggle caption Charles Moore/Black Star

Smoke and ash engulf the area around the World Trade Center. See a gallery of aerial images from Sept. 11. Greg Semendinger/NYPD via ABC News/AP hide caption

itoggle caption Greg Semendinger/NYPD via ABC News/AP

An elder of the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS) poses with his family, including his 5 wives. See a gallery of Stephanie Sinclair's photos. Stephanie Sinclair/National Geographic hide caption

itoggle caption Stephanie Sinclair/National Geographic

James Dean walks through a rainy Times Square. Dennis Stock/Magnum Photos hide caption

itoggle caption Dennis Stock/Magnum Photos