What is the world’s most dangerous toy? Probably the Gilbert U-238 Atomic Energy Lab Kit, which included three sources of radiation and four uranium ores that are also radioactive. The kit, which first went on sale in 1950, came with an instruction booklet, a pamphlet on how to prospect uranium, and various tools that enabled children to dive deep into the world of atomic chemistry. Voula Saridakis, a curator at the Chicago Museum of Science and Industry, explains the fascinating history of this rare toy.