The Moon is a geochemically differentiated object. It has a feldspathic crust (highlands regions) composed of three petrological suites. Underlying that crust is a compositionally heterogeneous upper mantle from which ferrobasalts and picrites (mare regions) were generated. Lunar samples retain a memory of the time-dependent flux of meteorites and comets, which has implications for the origin of sustainable life on Earth and the orbital evolution of the outer planets. Permanently shadowed regions at the lunar poles may contain reservoirs of volatile ices, which would have important resource potential for scientific bases. Geophysical data show that the Moon has a thick, seismically active lithosphere, a partially molten zone beneath that lithosphere, and a small metallic core. The pace of scientific exploration has quickened since 2003 with the successes of spacecraft from Europe, Japan, the People's Republic of China, and India. Upcoming launches of spacecraft from these same nations and the United States herald a new era of lunar discoveries.