As the number of publicly funded early childhood education (ECE) programs increases, policymakers will need empirical evidence to justify the taxpayer investment. Such justification will require a stronger understanding of the essential components of an ECE program's design, as well as solid evidence on which components, or constellations of components, are most effective in achieving strong outcomes for specific subgroups of children. Expectations for child outcomes must be based on the realities of the program components, the target populations, and the financial and human resources that support program implementation. The need for more robust quantitative and qualitative data to ensure stronger outcomes for all young children and significantly narrow the opportunity and achievement gap for minoritized children and those living in poverty. Believing in magic will not produce strong outcomes (Brooks-Gunn, 2003). Overpromising and underdelivering will have catastrophic results for the children and families who might benefit most from ECE initiatives. This volume asserts that randomized controlled trials (RCTs) could be greatly enhanced by the findings from rigorous empirical data that provide contextual information about the participants, the settings, and the overall conditions under which the treatment is conducted. Throughout this volume, this type of analysis is referred to broadly as implementation research. However, the intent is not to provide a single definition of implementation research. Rather, the hope is to initiate a conversation that is centered on what else needs to be explored about how ECE programs are operationalized and what shape the research might take.