For several decades, Harvard physics professors have shared a small block of uranium with their students. In 1939, as Germany invaded Poland, the Nazi government secretly initiated a nuclear program. In late 1944, as Allied forces approached, a group of German nuclear physicists working for the Nazi government moved their laboratory to a cave beneath a castle in the small town of Haigerloch. Fortunately, given the Nazi regime’s aims and the unlimited nature of that global war, their scientific inquiry fell short. Rather than documenting a toll of potentially millions more lives lost, the small cube of uranium now resides in Harvard’s collection, cased in lead, ready to teach about geopolitics, history, and scientific processes.