Children in Kawamata, Japan, take potassium iodide on Monday to protect against thyroid cancer after being evacuated from the vicinity of the Fukushima Daiichi Nuclear Power Plant. Asahi Shimbun via Getty Images hide caption

itoggle caption Asahi Shimbun via Getty Images

This young patient from India received his cornea transplant in 2009, when he was 10. Here he is shown before (above) and after (below) the transplant, which he received at the LV Prasad Eye Institute (LVPEI), SightLife's partner center in Hyderabad, India. Courtesy of LVPEI hide caption

itoggle caption Courtesy of LVPEI

Institute for Marine Mammal Studies veterinary technician Wendy Hatchett takes a skin sample from a dead bottlenose dolphin that was found on Ono Island, Ala., and brought for examination to Gulfport, Miss., on Tuesday. Patrick Semansky/AP hide caption

itoggle caption Patrick Semansky/AP

Scientists hope to use a fungus to keep malaria-carrying mosquitoes like the Anopheles gambiae species from growing resistant to insecticides. Courtesy of James Gathany/CDC hide caption

itoggle caption Courtesy of James Gathany/CDC

Not all young girls avoid dirt. Hannah Rose Akerley, 7, plays in a gigantic lake of mud at the annual Mud Day event in Westland, Mich., last July. Bill Pugliano/Getty Images hide caption

itoggle caption Bill Pugliano/Getty Images