Understanding the structure of materials is one of the most important stages of production in various industries (particularly, in the food industry, metallurgy, chemical industry, mineralogy, thin films and ceramics production), as well as in the scientific field of activity. It should be noted that studies of changes in the crystalline structure of samples, deformations, identification of samples, quantitative analysis of the content of components in materials, and changes in their physical and chemical properties under the influence of various external conditions are important too. X-Ray diffraction is used for the investigation of crystalline materials. The principle of diffractometers operating and their types are described. It is shown that X-ray diffraction is often used for studying the processes of sintering of metals, determining the shelf life of substances, quality control of food. The scale of of this method application is highlighted.