In recent years, there has been rapid growth in the research field of real-time observation of nuclear and electronic dynamics in molecules. Its time range extends from femtoseconds to attoseconds. This has been made possible by the development of both laser technology and time-dependent theoretical treatments. Indeed, this research field is arguably the most active one in molecular science, second only to femtosecond chemistry. The outcome of the research is expected to make an important contribution to physics, materials science and biology as well as chemistry. In this monograph, the...