Persistent Identifiers (PIDs) are essential for ensuring the Findability, Accessibility, Interoperability, and Reusability (FAIR) of research outputs. By providing rich, standardized, and machine-readable metadata with long-term availability, PIDs enable detailed description of a large number of (research) resources such as data, publications, code, persons, institutions, projects, grants, and so on. Their impact spans the entire research life cycle, from funding applications to publication and reuse of outputs, offering numerous advantages for researchers and infrastructure providers alike. The PID4NFDI project is a basic service within the German National Research Data Infrastructure (NFDI) and is currently in its second funding phase (integration). Its overarching goal is to consolidate, harmonize, and evolve the PID service landscape across NFDI at technical, organizational, methodological, and communication levels.