A "wiggler" is an insertion device used for spatially concentrating radiation for research purposes, and an "undulator" is a multi-period wiggler. Undulator and wiggler devices are inserted in a free straight section of the storage ring of the synchrotron. This book explores the radiation produced by these insertion devices, the engineering and associated beamline instrumentation, and some applications. The authors cover topics from a variety of fields, such as solid state physics, biology, biomedical systems, polarization modulation spectroscopy, optical engineering, and metrology. Their treatment of the subject will undoubtedly stimulate readers' interest in the many applications of insertion devices.