This book provides a comprehensive treatment of the concepts and applications of digital twins and related virtual prototyping technologies for a variety of distributed Internet-of-Things (IoT) applications. It can serve as a reference for practitioners to understand the scope and limitations of these complex technologies and how they can be used in a range of real-world applications. It can also be used as a starting point for researchers interested in exploring this area. The range of applications covered includes transportation, healthcare, manufacturing, and many others.