To understand a living system, such as a tree, in an ecologically systemic way involves more than simply reducing the tree down to its parts or by analyzing the tree from part to whole. Not only does one need to study the tree's leaves, stems, branches, trunk, root system, and its interaction with the environment but from many vantage points to make sense of how each part exists in dynamic relationship with the others as an integrated system. The same is true about the purpose of this book. It is not meant to be a recipe for how to teach mathematics well or to serve as simply a descriptive account of a teaching practice. It is in essence, a systemic exploration into the embeddedness and co-emergence of theory and practice in mathematics teaching. This book is ideal for undergraduate and graduate courses in mathematics education and curriculum studies. With its up close and contextual forms of data and a variety of interpretive methods used for the analyses, this book is highly suitable for courses in research. The audience includes professors, teacher educators, and in-service teachers who are interested in ecological theories and how these inform mathematics teaching and learning.