This book covers the physics and technology of short pulse laser sources that generate pulses with widths of only a few optical cycles. The basic design considerations for the different systems, such as lasers, parametric amplifiers and external compression techniques, which have emerged over the last decade, are discussed to give researchers and graduate students a thorough introduction to this field. The existence of these sources has opened many new fields of research that were not possible before, such as UV- and X-ray generation from table-top systems using high-harmonic generation, frequency metrology with unprecedented precision, high-resolution optical coherence tomography and strong-field ultrafast solid-state processes, to mention only a few. Many new applications will follow. The book attempts to give a comprehensive, while not excessive, introduction to this exciting, new field that serves both experienced researchers and graduate students entering the field.