Abstract
We introduce a research field in which coherent, x-rays (including extreme-ultraviolet light) are generated
based on a free-electron laser (FEL) using laser-plasma electron acceleration. A brief formulation of
the self-amplified spontaneous emission (SASE) FEL is given and the required electron beam parameters
for an SASE FEL in the X-ray region are discussed. We also present experimental activities in the world
and simulation modeling.