Engineering the perfect cookie: You can control the diameter and thickness of your favorite chocolate chip cookies by changing the temperature of the butter and the amount of flour in the dough. Morgan Walker/NPR hide caption

itoggle caption Morgan Walker/NPR

A young girl stands in the doorway of a home in Uttar Pradesh, India. The markings on the door show that a polio immunization team vaccinated children in the home. Alyce Henson/Courtesy of Rotary International hide caption

itoggle caption Alyce Henson/Courtesy of Rotary International

Click to see an interactive map of Meriden, N.H., with stories from Okkervil River's Will Sheff about his childhood there. William Schaff hide caption

itoggle caption William Schaff

Click to see an interactive map of Meriden, N.H., with stories from Okkervil River's Will Sheff about his childhood there. William Schaff hide caption

itoggle caption William Schaff

Bobbie Hanvey and his son Steafán Hanvey, in Northern Ireland. Courtesy of Peter Muhly hide caption

itoggle caption Courtesy of Peter Muhly

Sonny Vaahn, 25, holds his family's refugee identification in Bronx, N.Y. The card was issued to them during their initial entry into a refugee camp along the Thai-Cambodian border after the "killing fields" atrocities ended in Cambodia. Courtesy of Pete Pin hide caption

itoggle caption Courtesy of Pete Pin

Ricardo Galvez, Giovanna Meneses Pisco and Arely Betzabe pose for a photograph in front of their former home El Ayllu. The family was back in the neighborhood to gather some of their belongings, and Giovanna spent the hours teary-eyed. As soon as families moved out, the Ministry of Transportation and Communications, with the help of paid community members, began to demolish the buildings. Courtesy of Elie Gardner hide caption

itoggle caption Courtesy of Elie Gardner