Site-specific mutagenesis of DNA, developed some thirty years ago, has proven to be one of the most important advances in biology. By allowing the site-specific replacement of any amino acid in a protein with one of the other nineteen amino acids, it ushered in the new era of "Protein Engineering". The field of protein engineering has, however, evolved rapidly since then and the last fifteen years have witnessed remarkable advances through the use of new chemical, biochemical and molecular biological tools towards the synthesis and manipulation of proteins. The chapters included in this book reflect the rapid evolution of protein engineering and its many applications in basic research, biotechnology, material sciences and therapy. This book will provide the reader with an introduction to state-of the-art concepts and methods and will be of use to anyone interested in the study of proteins, in academia as well as in industry.