I heard that it is possible to measure positions of individual atoms in a crystal. Is this true? I understand the principle of measuring crystal orientation and base vectors of Bravais lattice with X-ray, but I have no idea how positions of individual atoms can be obtained. I suppose it is only possible to measure the geometry of Bravais lattice of each small piece of the crystal, assuming that the small piece has aproximately periodic structure over many atom distances. But what about the areas with lots of defects (for example grain boundaries) or large deformations? Is it possible to obtain information about the positions of individual atoms in those parts of the crystal?