This book brings together leading researchers in mathematics education to share personal narratives of key mathematical moments or ideas that inspired, surprised, or helped direct their research. While the fruits of research activities and products are shared at scholarly conference and journals, the footprints of mathematics that ignited the research processes is often behind the scenes and only acknowledged informally. To make mathematics -- an essential component and a determining driving force of mathematics education research -- more visible, chapters in this book highlight the indispensable and indisputable role of mathematics in mathematics education research. The book is unique and timely in addressing the essential, but increasingly side-lined, role of mathematics that permeates mathematics education research journals, graduate programs, and the personae of the next generation in the profession. It renounces the shift away from mathematics and attempts to restore the place and value of mathematics by presenting elegant, intriguing, and substantial contributions to mathematics education that have come from keeping mathematics at the core of research pursuits. Each chapter shares a journey in mathematics education research that was inspired by an affinity for mathematics, and that helped shaped the field as we know it. Each author shares insights and reflections on the status of mathematics in the mathematics education community, how it has changed, and what further changes might be expected. This edited volume is of major interest to the mathematics education community, including mathematics educators, teacher educators, researchers, professional development providers, and graduate students.