This book provides a summary of the state of science in teh field of single particle detection and measurement. The text delineates between those low performance detectors, capable of registering only a large number of particles and those complex, highly designed systems capable of detecting and measuring single interactions or events. The author describes the problems associated with detection, measurement and subsequent interpretation of such quantum processes. He also evolves the subject from its roots in nuclear and particle physics into latter day applications such as probes for investigation of materials and objects. The different nature and use of high-energy particles compared with photons is highlighted.