The book deals with the description of the complex phenomena of diesel injection processes. It begins with the description of the most used injection systems: common rail and pump injector, explains how they work, especially injector running. Afterwards, the nature of the flow inside the injector nozzles is analyzed. Special attention is given to cavitation phenomena which can dramatically affect the characteristics of the flow at the injector outlet and so affects the following processes: atomization, air entrainment and vaporization. These phenomena are also studied in detail in the book. The authors highlight the main results in the literature on these subjects and also contribute their own research. High quality illustrations are used in the book, which helps readers understand the topics. The reader will learn about the different processes involved in Diesel injection, the physics behind those processes and finally the tools, either experimental or computational, that are normally used to characterize them.