A cross-section of skeletal muscle in this light micrograph shows the individual, parallel muscle fibers (red). These fibers work in concert to power movement. Thomas Deerinck, NCMIR/ScienceSource hide caption

itoggle caption Thomas Deerinck, NCMIR/ScienceSource

Oklahoma Gov. Mary Fallin issues a statement to the media after the execution of Clayton Lockett. Oklahoma Secretary of Safety and Security Michael C. Thompson stands behind her at the Oklahoma State Capitol in Oklahoma City. Alonzo Adams/AP hide caption

itoggle caption Alonzo Adams/AP

Loved ones express their grief at the burial of Ramon Romero Ramirez in Chichigalpa, Nicaragua, January 2013. The 36-year-old died of chronic kidney disease after working in the sugar cane fields for 12 years. Ramirez is part of a steady procession of deaths among cane workers. Ed Kashi/VII hide caption

itoggle caption Ed Kashi/VII

Mike Smith, of Long Beach, Calif., now pays $200 for his family's health insurance policy, compared with the $3,000 a month he would have had to pay on the individual market last year. Stephanie O'Neill for NPR hide caption

itoggle caption Stephanie O'Neill for NPR

Tornadoes killed at least 17 people on Sunday and Monday. But some managed to stay safe in underground shelters like the one at right in Vilonia, Ark. Karen E. Segrave/AP hide caption

itoggle caption Karen E. Segrave/AP