Structural biologists create crystals of proteins, shown here, as a first step in a process called X-ray crystallography, which can reveal detailed, three-dimensional protein structures. Protein crystallization is the process of formation of a protein crystal. While some protein crystals have been observed in nature, protein crystallization is predominantly used for scientific or industrial purposes. X-ray crystallography is a tool used for identifying the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder and various other information.