A technique used to determine the detailed, three-dimensional structure of molecules. It is based on the scattering of X-rays through a crystal of the molecule under study. The X-ray Crystallography was first applied in 1961 by J. Kedrew & M. Perutz. The technique was also used to define the shape and structure of proteins.

Short wavelength energy beams capable of penetrating most substances except heavy metals. X-rays are widely used in imaging and therapy.