Water is an essential ingredient of life, and is necessary for a future human station or colony on the moon. In addition, knowing H2O concentration in a planetary body offers clues for its origin and evolution. This inaugural lecture will focus on our recent work of the H2O content on the surface and in the interior of the moon. Even though there is no liquid water on the moon, water ice has been found in permanently shadowed impact craters in the lunar polar region. Our studies show that both lunar surface soil and lunar interior likely contain about 100 ppm of H2O. Lunar soil water is inferred to be mostly from solar wind implantation, and interior water is largely primordial. These results point out ways for in situ extraction of water on the moon and other airless planetary bodies, and provide constraints on the Giant Impact Hypothesis for the origin of the moon, as well as its evolution.