This book is modeled after Jim Burke's successful Common Core Companion Series. It is the first of two books (K-2, 3-5) in the series. The book will include a clear explanation of the mathematics within each domain, cluster, and standard and suggested grade level appropriate visual models and representations. It is a book for math teachers who may or may not be math specialists. As teachers plan and develop their curriculum, this book will help them determine important mathematics in a cluster and how that mathematics connects from one grade to the next as well as within a grade.