The papers in this volume cover the major areas of research activity in the field of ultrafast optics at the present time, and they have been selected to provide an overview of the current state of the art. The purview of the field is the methods for the generation, amplification, and characterization of electromagnetic pulses with durations from the pieo-to the attosecond range, as well as the technical issues surrounding the application of these pulses in physics, chemistry, and biology. The contributions were solicited from the participants in the Ultrafast Optics IV Conference, held in Vienna, Austria, in June 2003. The purpose of the conference is similar to that of this book: to provide a forum for the latest advances in ultrafast optical technology. Ultrafast light sources provide a means to observe and manipulate events on the scale of atomic and molecular dynamics. This is possible either through appropriate shaping of the time-dependent electrie field, or through the ap­ plication of fields whose strength is comparable to the binding forces of the electrons in atoms and molecules. Recent advances discussed here include the generation of pulses shorter than two optical cycles, and the ability to measure and to shape them in all degrees of freedom with unprecedented 2 21 2 precision, and to amplify them to the Zettawatt/cm (10 W /cm ) range.