Research Findings: We are in the midst of a revolution. Prior to the onset of the 21st century, mathematics education in the United States was deemphasized (Geary, 1996), and mathematics as an instructional subject has traditionally been considered above the preschool and kindergarten levels. However, the old regime--the knowledge and philosophies that governed mathematics and early childhood education theory in the last century--has been overthrown. Today, developmental psychologists have begun to map out the specific pathways of mathematical knowledge development from birth to age 8. We now know that prior to elementary school, young children engage in surprisingly complex intuitive mathematical thinking in the areas of number, geometry, measurement, algebraic thinking, and data analysis (for reviews, see T. C. Cross, T. A. Woods, & H. Schweingruber, 2009; J. Sarama & D. H. Clements, 2009). With increased recognition of the importance of early mathematics for later academic success, early childhood mathematics education is now a national priority. Practice or Policy: This article discusses the history, research, and political impetus for the shift in paradigm; the current status of the early childhood mathematics education movement; and the implications for young children and teachers in the United States.