Book excerpt: The authors of this book, all with a background in condensed matter physics, have carried out advanced researches in recent years to study the optical and magneto-optical properties of many kinds of new functional materials, including metal-based metamaterials, narrow-to-wide-bandgap semiconductors, thin films, and magnetic and magneto-optical materials by using different types of optical methods and instruments. This book describes some of the more recent progresses and developments in the study of condensed matter optics in both theoretic and experimental fields. It will help readers, especially graduate students and scientists who are studying and working in the nano-photonic field, to understand more deeply the characteristics of light waves propagated in nano-structure-based materials with potential applications in the future.