Leading experts introduce important topics in high field laser physics, including high harmonics generation from laser-gas interaction, propagation of ultrashort laser pulse in air, physics of relativistic laser plasma interaction, acceleration of electrons and ions driven by intense lasers, laser-driven x-ray sources, physics of fast ignition with intense lasers. This book covers the involved fundamental physics, the recent advances, and the prospects of future applications. It is very useful to graduate students, young researchers, and people who want to have an overview of this field.