Key features: ·         Provides a clear introduction to modern ultrafast phenomena and their applications in physics, chemistry, materials sciences, and engineering. ·         Presents in detail how high-harmonic generation occurs in atoms and solids. ·         Explains ultrafast demagnetization and spin switching, a new frontier for development of faster magnetic storage devices. ·         Includes numerous worked-out examples and problems in each chapter, with real research codes in density functional theory and quantum chemical calculations provided in the chapters and in the Appendices. This book is intended for undergraduate and graduate students, researchers in physics, chemistry, biology, materials sciences, and engineering.