At the end of World War II, atomic bombs were dropped on Hiroshima and Nagasaki. The ensuing fires in the cities blew huge amounts of radioactive material and soot into the air, causing so-called "black rain." How extensive was the rainfall? The latest scientific findings are shedding light on this question and may help people not legally recognized as hibakusha, or atomic bomb survivors, win full medical support. Seventy-nine years after the bombings, we follow the efforts of scientists and interview those fighting for government recognition.