This book presents a unique approach to non-perturbative Quantum Many Body Physics. Instead of focusing on the standard approaches, it builds our understanding of these systems by using methods that traditionally pertain to few-body physics, allowing for strong interactions to be tackled from a solid and well-understood foundation. The covered topics range from exactly solvable models, which are known to require only two-particle input, and Bose-Fermi mappings, which are fully non-perturbative, to the physics of few-body systems embedded in many-body media. The book is intended as a detailed advanced tutorial for young and experienced researchers that want to delve deeper into this exciting field.Key Features: Many worked examples of representative quantum systems, together with their physical interpretations and the main consequences of their solutions. Set of problems at the end of each chapter, not meant to complement the theory, but to give the reader dexterity in using the chapter's methodologies. Timely discussion of a recently developed, and very active field summarised as "From Few- to Many-Body Quantum Physics of Strongly Interacting Particles", and the physics of interacting quantum systems in inhomogeneous media. First, coherent, detailed monograph on the theory and methods of the field. Presents a rigorous account of the modern approaches to low-energy collisions and their use in few- and many-body physics, which have not appeared in book format. The book is relevant to a wide range of researchers and advanced students, from atomic and condensed matter physics, to photonics and nuclear physics. Written by pioneers and true experts in the field