This book illustrates the significance of various optical spectroscopy and microscopy techniques, including absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, and Raman spectroscopy for deciphering the nature of biological molecules. The content of this book chiefly focuses on (1) the principle, theory, and instrumentation used in different optical spectroscopy techniques, and (2) the application of these techniques in exploring the nature of different biomolecules (e.g., proteins, nucleic acids, enzymes, and carbohydrates). It emphasizes the structural, conformational and dynamic, and kinetic including the changes in biomolecules under a range of conditions. In closing, the book summarizes recent advances in the field of optical spectroscopic and microscopic techniques.