This book provides fundamental knowledge in the fields of attosecond science and free electron lasers, based on the insight that the further development of both disciplines can greatly benefit from mutual exposure and interaction between the two communities. With respect to the interaction of high intensity lasers with matter, it covers ultrafast lasers, high-harmonic generation, attosecond pulse generation and characterization. Other chapters review strong-field physics, free electron lasers and experimental instrumentation. Written in an easy accessible style, the book is aimed at graduate and postgraduate students so as to support the scientific training of early stage researchers in this emerging field. Special emphasis is placed on the practical approach of building experiments, allowing young researchers to develop a wide range of scientific skills in order to accelerate the development of spectroscopic techniques and their implementation in scientific experiments. The editors are managers of a research network devoted to the education of young scientists, and this book idea is based on a summer school organized by the ATTOFEL network.