This second edition is completely revised and improved and contains eight new chapters and six new appendixes. In addition to the theoretical background on light propagation through diffusive media, this update also provides new didactical material. Although the theoretical and computational tools provided in this book have their primary use in the field of biomedical optics, there are many other applications in which they can be used, including, for example, analysis of agricultural products, study of forest canopies or clouds, and quality control of industrial food, plastic materials, or pharmaceutical products, among many others.