Afghan metal workers put together billboards for Ghazni candidate Daoud Sultanzoi. The incumbent is seeking re-election to his seat in parliament. Soraya Sarhaddi Nelson/NPR hide caption

Megan Taylor grew up feeling she was living in the wrong body. In her 20s, she decided to do something about it. First, she changed her name to Miles. Courtesy of Miles Taylor hide caption

Yossele Rosenblatt is recognized as the greatest cantorial singer of all time. John Springer Collection/Corbis hide caption

Oxygen is carried by red blood cells, but a specific mutation can cause the cells to take on a sickle shape and make them inefficient at carrying oxygen.  This highly adaptive mutation spread through Africa once malaria became a problem there. EM Unit, UCL Medical School, Royal Free Campus/Wellcome Images hide caption

A wind turbine, generating power near Boston in 2006. Stephan Savoia/AP hide caption