Spectroscopy studies the interactions between matter and electromagnetic radiation. This is achieved by measuring radiation as a function of wavelength or frequency. Interactions of radiating energy with atoms, molecules and nuclei have led to the development of atomic, molecular and NMR spectroscopy. Other spectroscopic methods like auger spectroscopy, hadron spectroscopy, photoacoustic spectroscopy, spin noise spectroscopy, etc. are distinguished by their specific applications. Some of the practical applications of spectroscopy are measurement of different compounds in food, cure monitoring, toxic compounds measurement in blood samples, etc. This book provides comprehensive insights into the field of spectroscopy. It also traces the progress of this field and highlights some of its key concepts and applications. It is appropriate for students seeking detailed information in this area as well as for experts.