A key unknown in lunar science is to what extent the Moon is a melted, radially layered planet like Earth or a primordial unmelted relic of the early solar system, like many asteroids. Did the Moon form a metallic core and an ancient magnetic field? A new era of intensive lunar exploration is underway, providing major new insights into this decades-old question. Planetary scientist Ben Weiss, of the Massachusetts Institute of Technology, will review the current understanding of the lunar interior by sharing new results from spacecraft observations and studies of Apollo samples.