January 7, 1943 - October 25, 1955: Age 12
Sadako Sasaki was only 2 years old when the Americans dropped an atom bomb on her home city of Hiroshima. It blew her right out of her house, which later burned in the fires, but her mother picked her up and started running away from the destruction. As they were running they were caught in the "black rain" that followed the explosion.
Sadako and her mother survived the explosion, and she grew up healthy. She was the fastest runner in her school and dreamed of becoming a phys ed teacher when, in late 1954 at the age of 11, she caught a cold and developed small lumps in her neck. By January purple spots had appeared on her leg, and in February she was diagnosed with leukemia, the "atom bomb disease". Her doctor said she had a year at most.
During that summer, the people of Nagoya sent 1,000 origami cranes to the hospital to cheer patients up. Inspired by the cranes, and the saying that anyone who folded 1,000 cranes would be granted a wish, Sadako started folding her own cranes. When she ran out of paper, she scrounged more from medicine wrappings and labels, and gift paper from other patients. By late October she had folded more than 1,300 paper cranes. She died on the morning of October 25, 1955. Her last words were about some food her family had persuaded her to eat: "It's good."
The young people of Japan were deeply affected by the story of the young girl who folded cranes. They raised enough money to create a monument for her, and for all the other children who had been killed by the bombs. A large monument was built in the Hiroshima Peace Park, where to this day children bring folded paper cranes as an offering. At the foot of the statue is a plaque which reads, "This is our cry. This is our prayer. Peace in the world."
Sources: Wikipedia, World Peace Project for Children, Hiroshima Virtual Museum