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Preface The use of spectroscopic methods to examine biomolecules has a long and rich history. Such methods have the virtue of being largely noninvasive and capable of probing living materials as well as subcellular preparations and isolated biomolecules. The information gained is interpretable in terms of structural parameters and intramolecular interactions. Using time-resolved approaches, dynamics can be explored readily over a time range from less than a picosecond to seconds and longer. This permits ready exploration of intermolecular interactions and intramolecular motion relevant to biological processes. Advances in technology and methodology in spectroscopy have moved the field forward at a breathtaking pace in recent years. We have come a long way from the era when cytochrome oxidation state changes were monitored visually using a hand spectroscope or when absorption spectrometry was done using photographic detection. In this volume the reader can learn about instrumentation that uses diode array detectors to monitor absorption or emission spectral properties with great precision at hundreds of wavelengths simultaneously or Fourier transform methods that provide a significant increase in the efficiency of collecting and analyzing spectroscopic information distributed over a wide wavelength band. Mode-locked lasers and associated pulse-compression and continuum-generation techniques allow pulse-probe measurements of fast (to l0 fsec = l0 -~4 sec) absorption changes or fluorescence relaxation in the picosecond regime. Single-photon counting methods have greatly improved the signal-to-noise of optical detection systems for steady-state spectroscopy and especially for time-resolved fluorescence measurements. Pulsed lasers have advanced the application of time-resolved Raman spectroscopy and the ability to discriminate between Raman and fluorescence signals. In combination with the use of ultra