Materials are atomically divided into crystalline and amorphous materials. In crystalline materials, atomic order is maintained in all directions over long distances. The distance between the atoms is the same in all directions and does not change. In amorphous materials, however, this order is limited to a few atoms. In other words, in a short distance, the distance between the atoms is the same, but in another part of matter, the distance between the atoms may be different. Familiarity and study of the crystal structure of materials justifies the occurrence of many chemical and physical reactions. Crystallography The science of studying the formation, growth, study of external shape, internal structure and physical properties of crystalline materials.