The U.S. Department of Energy (DOE) has granted “Critical Decision-Zero” (CD-0) status to the sPHENIX project, a transformation of one of the particle detectors at the Relativistic Heavy Ion Collider (RHIC)—a DOE Office of Science User Facility at Brookhaven National Laboratory—into a research tool with unprecedented precision for tracking subatomic interactions. This decision is an important first step in the DOE process for starting new projects, stating that there is a “mission need” for the capabilities described by the proposal.