Protein structure determination. X-ray diffraction image revealing the structure of a protein. Spots (white) show the diffraction pattern that forms as X-rays pass through the protein. The diffraction occurs because the protein has been prepared in a crystalline form with its atoms forming a regular lattice arrangement. It is this lattice that makes the X-rays diffract, with waves of X-ray radiation reinforcing or destroying each other as they are disrupted by the protein's atoms. The structure of the protein determines the pattern seen, which allows complex mathematics to be used to determine the structure of the protein. The circular space and spot (lower centre) is the pattern's centre.