William W. Parson is an emeritus professor of Biochemistry and adjunct professor of Chemistry at the University of Washington. He received his undergraduate degree at Harvard University and doctorate in biochemistry at Western Reserve University. As a postdoctoral fellow in biophysics at the University of Pennsylvania, he began using pulsed lasers to study the early electron-transfer reactions of photosynthesis. This led to the demonstration that the light-driven reaction in photosynthetic bacteria is photo-oxidation of a bacteriochlorophyll complex that then draws electrons from a series of cytochromes. Parson continued these studies at the University of Washington using progressively faster techniques of laser and optical spectroscopy. As the sequence of electron-transfer steps emerged from this work and as crystallographers elucidated the structure of bacterial photosynthetic reaction centers, he began combining spectroscopic measurements with computational approachesand quantum mechanical theory to explore factors that determine the rate, specificity and temperature of electron transfer. He has continued work on the theory of electron transfer since becoming an emeritus professor. Professor Parson enjoyed teaching undergraduate and graduate students, mentoring postdoctoral fellows and collaborating with international colleagues. The present book began as a series of lecture notes for a course he taught for graduate students in molecular biophysics. Keeping the book up to date and expanding it into new areas continue to be sources of pleasure. Clemens Burda pursued his undergraduate studies at the University of Basel in Switzerland and continued graduate studies in photochemistry and laser spectroscopy under the guidance of Prof. Jakob Wirz. His early studies of ultrafast chemical reactivity led to the spectroscopic identification of short-lived intermediates including singlet- and triplet-statenitrenes. Other studies included the photochemistry of aromatic molecules in water, which led to the discovery of multiple reactive intermediates at a time when excimer and dye lasers were state of the art for achieving sub-picosecond time resolution. His growing interest in ultrafast spectroscopy led him to pursue postdoctoral studies in femtosecond spectroscopy with Prof. Mostafa El-Sayed at the Georgia Institute of Technology, working with the solid-state lasers, OPAs, and nonlinear optics that are now widely used in spectroscopy laboratories. Since 2001, Clemens Burda has been a professor at Case Western Reserve University, where he is the Chair of the Chemical Professorship and director of the Center for Chemical Dynamics and the Nanomaterials Research Lab. His interests include femtosecond time-resolved spectroscopy and imaging of molecules, semiconductor and metallic nanomaterials, and renewable energy development. Another major research pursuit is the development of imaging modalities to identify early-stage diseases, light-driven therapies, and their thermal management. Professor Burda is an enthusiastic educator who has graduated over 30 graduate students and enjoys teaching spectroscopy to students at all levels.