Roger Fu has transformed paleomagnetism through groundbreaking research that spans planetary formation, Earth history, and methodological innovation. His early work resolved a decades-old puzzle by demonstrating that the solar nebula possessed a magnetic field strong enough to drive accretion and angular momentum transport and by proving the existence of an early dynamo on an asteroid—fundamental advances in understanding the origins of our solar system. At Harvard, Fu pioneered the adaptation of quantum diamond microscopy (QDM) for geoscience, enabling magnetic imaging at nanometer scales with moment resolutions 4 orders of magnitude beyond previous techniques. This innovation has opened new frontiers, from detecting magnetization in ancient terrestrial rocks and meteorites to probing the magnetic history of Mars. His team’s work on the Allan Hills 84001 meteorite revealed evidence for a reversing Martian dynamo, reshaping views of planetary evolution. Fu’s research also addresses Earth’s earliest tectonic regime. By combining QDM with rigorous statistical methods, he demonstrated mobile-lid plate motion by 3.2 Ga and refuted claims of stagnant-lid tectonics based on zircon paleointensity data. His approach—transparent, data driven, and collaborative—sets a benchmark for integrity and scientific rigor. Beyond technical excellence, Fu exemplifies AGU’s core values. He shares all laboratory data, mentors a diverse cohort of graduate students and postdocs whose first-authored papers appear in leading journals, and actively engages in outreach and education. His intellectual breadth extends from quantum physics to cultural anthropology, as shown by his innovative study of magnetic anomalies in pre-Olmec sculptures, revealing early human awareness of magnetism. For his outstanding contributions to paleomagnetism—illuminating the magnetic history of the solar nebula, planetary dynamos, and early Earth tectonics while revolutionizing magnetic imaging—Roger Fu richly deserves the James B. Macelwane Medal. —Joseph L. Kirschvink, California Institute of Technology, Pasadena, California