This book is an ambitious attempt to bridge the infamous gap between theory and practice in control. The book has ten chapters, written by seasoned researchers from all over the world. It is organized in four parts: Large-scale Problems, Aerospace, Vision and Sound and Electromechanical, and covers a very wide range of problems from chemical reactors to magnetic bearings. In spite of the wide diversity of topics and authors a coherent presentation is obtained by a uniform organization imposed by the editors. Each chapter begins with a brief summary of the theory and a - scription of the application, followed by results of simulations or experiments and conclusions. The problem descriptions and the discussions about the relevance of the theory are more detailed than presentations normally found in papers. The book is a nice complement to traditional textbooks and the wide range of topics illustrate the richness and ubiquity of identi?cation and control. Santa Barbara, California, USA KarlJohanÅström March 2007 Preface System theory, in particular, automatic control and system identi?cation have ex- rienced a fast evolution in the past decades. Many new methods have been dev- oped, performance requirements in traditional engineering areas have signi?cantly increased and new and more demanding applications in other areas of engineering and science have appeared. Many textbooks have been written that present the r- evant theory and sometimes "practical" examples to which the theory has been - plied.