In the volcanic hot springs of northern California, a microscopic organism has quietly dismantled one of biology's long-held boundaries. Scientists supported by NASA have identified an amoeba — a complex, nucleated cell — capable of reproducing at temperatures previously thought lethal to all such life, suggesting that the architecture of complexity is more resilient than we imagined. Named Incendiamoeba cascadensis, this single-celled creature invites us to reconsider not only the limits of life on Earth, but the conditions under which life might persist elsewhere in the cosmos.