This book describes the experimental foundations of particle detectors and their application in experiments. The development of detectors is an important component of particle physics, astroparticle physics, and nuclear physics, and thus is part of the craft of experimental physicists in these fields. This comprehensive work includes all the material for corresponding master's modules in experimental particle physics, but also goes beyond that in content. The target audience is students who wish to delve deeper into the subject, as well as educators and researchers who can use the book as an introduction to scientific work on detector developments. The aim of the book is to present the physical principles for the detectors and their various designs as clearly as possible and as thoroughly as necessary.