The document outlines the structure and content of a book about learning in 3D environments called "Learning in 3D". The book is divided into four parts that explore the possibilities of 3D learning, build a blueprint for designing 3D learning experiences, discuss breaking new ground by moving beyond traditional instructional design models, and consider the future of 3D learning. Each part contains multiple chapters that delve deeper into topics like immersive learning technologies, designing learning experiences through different archetypes, and best practices for adopting enterprise 3D learning solutions.