The NHLBI Career Transition Award (K22) aims to support highly qualified postdoctoral fellows and doctoral-level researchers currently training within the NHLBI Division of Intramural Research. Its core objective is to facilitate their transition to independent junior investigator positions at extramural institutions. The grant provides a two-phase support model: a mentored intramural phase (up to two years) followed by an independent extramural phase (three years). Applicants must propose to serve as the lead investigator of an independent clinical trial, a clinical trial feasibility study, or a separate ancillary study to an existing trial. This is a SECTOR-SPECIFIC grant focused on biomedical, behavioral, and clinical research relevant to heart, lung, and blood diseases. The geographic scope is limited to the United States (including U.S. Territories and Possessions), as foreign organizations are not eligible to apply. This is a recurring grant opportunity, reissued from PAR-22-040, with multiple application deadlines each year until its expiration date.