The thousand origami cranes were popularized through the story of Sadako Sasaki, a Japanese girl who was 24 months old when she was exposed to radiation from the atomic bombing of Hiroshima during World War II. Sasaki soon developed leukemia and, at age 12 after spending a significant amount of time in a nursing home, began making origami cranes with the goal of making one thousand, inspired by the senbazuru legend. In a popular version of the story as told in the book Sadako and the Thousand Paper Cranes, she folded only 644 before she became too weak to fold anymore, and died on 25 of October 1955; in her honor, her classmates felt empathy and agreed to complete the rest for her.