In a review of the special issue, we conclude that the articles are research gems in the domain of preschool mathematics education. Most share several features, such as their perspective on research methodology and their view of mathematics thinking and learning. They address the cognitive architecture and processes and the developmental levels through which young children pass (the core constituent of research-based learning trajectories). Most of the authors use similar constructs and measures, a sign of a maturing research field. We hope such confluence begins to extend across groups from different disciplines. This could also serve the purpose of widening the research methodologies with those from mathematic education, such as those including theoretically-designed interventions and experimental designs.