The use of x rays has moved in the forefront of science and technology in the second half of the 20th century. This progress has been greatly stimulated by the advent of synchrotron x-ray sources in the 1960s. The undulator-based synchrotron radiation sources which have appeared in the last decade of the 20th century gave a new impetus to such development. The brilliance of the x-ray sources has increased by 12 orders of magnitude in 40 years and...