In this article, I explore the history of biological materials that scientists and physicians collected from those who survived the atomic bombings at Hiroshima and Nagasaki. Originally acquired beginning in 1946 to track the genetic effects of radiation in the offspring of atomic bomb survivors, these materials gradually became relevant to other kinds of biological and biomedical research. Many of the samples still held at the Radiation Effects Research Foundation are from individuals (approximately 65 percent) who are no longer alive. To scientists and others engaged with their management and use, these samples are uniquely valuable, timeless, a legacy for “all mankind.” Like materials taken from isolated populations around the world, the atomic bomb samples are both unique and universalized. They join other forms of Big Data in their seamless transition from dramatic specificity to general relevance. My paper explores what such legacies mean, and what they might teach us about the history of biology, the practices of biobanking, and the post-1945 Pacific world. This essay is part of a special issue entitled Pacific Biologies: How Humans Become Genetic , edited by Warwick Anderson and M. Susan Lindee.