Using Central Conceptual Structure theory as an heuristic, learning sequences in the acquisition of number knowledge are described in three forms that bridge theory and practice: as a four-stage theoretical progression, as items on a developmental test created to test the theoretical progression, and as learning objectives in a curriculum designed to teach math concepts and skills implied in the theoretical progression. Other aspects of the theory that were used to create teaching methods and materials for the Number Worlds curriculum are also described, as are some of the outcomes of this theory-based program.