1906, Barkla successfully polarized x-rays, confirming their wave nature. 1907, Mutation by x-ray reported in toads by Bardeen.
In 1912, Max von Laue predicted and discovered that x-rays could be diffracted by crystals.The hot cathode x-ray tubes and tungsten targets permitting higher voltages, first introduced by Coolidge in 1913.
Tomography developed in 1931. In 1948, First experimental x-ray image intensifier developed by Coltman. And in 1972, The CAT scanner (based on x-rays) was invented by Godfrey Hounsfield.
X-rays are part of the electromagnetic light specturm.