Spatial representation and thinking have evolutionary importance for any mobile organism. In addition, they help reasoning in domains that are not obviously spatial, for example, through the use of graphs and diagrams. This article reviews the literature suggesting that mental spatial transformation abilities, while present in some precursory form in infants, toddlers, and preschool children, also undergo considerable development and show important individual differences, which are malleable. These findings provide the basis for thinking about how to promote spatial thinking in preschools, at home, and in children's play. Integrating spatial content into formal and informal instruction could not only improve spatial functioning in general but also reduce differences related to gender and socioeconomic status that may impede full participation in a technological society.