This book is designed as a travel guide. The first part includes all the traditional sections from the ‘front end’ of a travel guide, including some basic vocabulary, tips, and a historical section about some of the pioneers of Lean in Engineering. The journey begins in the second part, which explains a number of Lean Engineering practices in some detail and the best itineraries to develop better products, discussing the underlying intentions and offering advice for implementation. Numerous concrete cases illustrate this part with case material drawn from the authors’ own experiences. Part Three is a brief guide to where and how to get started. Currently, there are no books on Lean Engineering written by practising engineers who have themselves experienced the adjustment of Lean principles to the business and challenges of new product development. The authors describe tools and practices that have already been widely tested and improved by many engineers with different cultures and skills in the Thales Group and other companies. Lean Engineering as we describe it has thus been able to demonstrate its effectiveness for several years. In addition, the authors describe new unique practices invented within the framework of their activities and which thus do not exist anywhere else (e.g., causal influence diagram (CID), Pull-Scheduling Board).