The Laboratory's main mission is national security, primarily ensuring the safety and reliability of the U.S. nuclear deterrent. The Defense Gallery features an exhibit about that work, called Stockpile Stewardship. Artifacts include a W80 warhead, air-launched cruise missile, Mark 12A, B61 and B83 bombs, and Fat Man, a bomb casing identical to the one dropped on Nagasaki and similar to the device tested at Trinity.