Overview: PRIMA has been selected for Phase A studies as a NASA Probe-class mission. PRIMA would be a cryogenically-cooled, far-infrared observatory for the community for the next decade. The hardware specifications and the capabilities of PRIMA are still under formulation. Key areas of study include the trade between resolving power, wavelength coverage, and mapping speed for low-resolution spectroscopy (24-235 μm, R >85), as well as the potential for medium-resolving-power spectroscopy (R ~4,400) and polarimetric imaging from 80-261 μm. PRIMA addresses all 3 science goals for a far-IR Probe from the National Academy of Sciences Astronomy 2020 Decadal Survey: 1. Tracing the astrochemical signatures of planet formation 2. Probing the co-evolution of galaxies and their supermassive black holes across cosmic time 3. Measuring the formation and buildup of galaxies, heavy elements, and interstellar dust from the first galaxies to today