Sune Svanberg is a professor of physics and head of the Atomic Physics Division of the Lund Institute of Technology. He is also the director of the multi-disciplinary Lund Laser Centre at the Lund University. He has extensive research experience in radiofrequency, optical and laser spectroscopy, and in the use of lasers in combustion diagnostics, environmental monitoring, and medical diagnostics and treatment, and is thus in good position to cover the vast scope of the book. Sune Svanberg has coauthored almost 500 papers and trained a large number or undergraduates and graduates in basic and applied atomic and molecular spectroscopy. He served extensively in international organisations and scientific advisory committees. He is a member of five academies and holds three honorary doctor degrees.