Volume 60 of Reviews in Mineralogy and Geochemistry assesses the current state of knowledge of lunar geoscience, given the data sets provided by missions of the 1990's, and lists remaining key questions as well as new ones for future exploration to address. It documents how a planet or moon other than the world on which we live can be studied and understood in light of integrated suites of specific kinds of information. The Moon is the only body other than Earth for which we have material samples of known geologic context for study. This volume seeks to show how the different kinds of information gained about the Moon relate to each other and also to learn from this experience, thus allowing more efficient planning for the exploration of other worlds.