On July 16, 1945, the Trinity test in New Mexico, the world's first nuclear explosion, generated extreme conditions that created an "impossible" crystal. Scientists have identified a previously unknown calcium copper silicate type-I clathrate, a cage-like crystal structure, within trinitite, the glassy material formed by the blast. This clathrate, discovered near a quasicrystal found in 2021, formed under transient pressures of 5 to 8 gigapascals and temperatures exceeding 1,500 degrees Celsius. The discovery marks the first clathrate confirmed among nuclear explosion products and offers insights into materials formed under extreme, rare conditions, potentially aiding in understanding nuclear testing effects and developing forensic tools. The findings were published in the Proceedings of the National Academy of Sciences.