In this monograph, the importance of fluctuations forbiological reactions is discussed from various points of view. Understandingthe biological reactions at the molecular level is one of the major targets inmany scientific fields, including not only basic biology but also physics,physical chemistry, and medical science. One of the key factors in the processis “fluctuation”. Thermal energy causes biological molecules to be in constantfluctuation even while they are carrying out their biological functions. How dobiological systems overcome the thermal fluctuations to realize thephysiologically relevant reactions? Scientists in a number of fields—physics,chemistry, pharmacology, medicine, and others—have contributed chapters thatelucidate the nature of the fluctuations and the relationship betweenfluctuations and biological functions. The fluctuations discussed in this volumeare detected by the transient grating method, nuclear magnetic resonance, X-raydiffraction and scattering, and computer simulation, among other methods. Thebook presents various results of the studies of fluctuations in biologicalprocesses that were obtained with these methods by the leading scientists intheir fields.