Children learn mathematics most effectively in contexts that are meaningful to them. In order to realize the potential of those contexts for fostering young children's mathematical learning, knowledge or mathematics as well as child development is the way to nurture and challenge children's thinking. Avoiding the debates surrounding 'hands-on' learning vs. direct instruction, the author focuses on the value of different contexts for learning and illustrates ways to genuinely engage children as active learners. The work is rich with examples of children's interactions with each other and with adults as they utilize and extend their understanding of mathematics. Examples and guidelines for developing lessons and activities will be useful to educators and parents.