Light, or electromagnetic wave, is the most powerful tool for probing the quantum mechanical motions of electrons and nuclei within molecules and condensed matter. Optical Processes in Solids describes the principles of this spectroscopic study with the help of illustrative comparisons of theoretical and experimental results that take into account the revolutionary progress brought about by the use of intense lasers and high-energy synchrotron light. In the final chapter Yutaka Toyozawa presents a speculative scenario on how solar light may have caused chemical reactions among atoms and molecules, leading to the creation and evolution of life on earth.