The long-held fascination with natural fluid inclusions in minerals is alive and well, partly as a result of new analytical techniques. The fluids and precipitated crystals in these submillimeter-dimension inclusions could yield evidence of the last stages of crystallization of their host minerals. They are remnants of the fluids with which the mineral was in equilibrium. Thus they could be highly valuable in the interpretation of hydrothermal mineral and ore deposits, metamorphic and igneous deposits, and petroleum-bearing rocks.