The aim of the 2018 edition of the Italian Association for Crystallography (AIC) International Crystallography School (AICS2018) is to give an overview on the characterization of polycrystalline materials through X-ray Powder Diffraction. Over the last twenty-five years, the advances in laboratory X-ray powder diffraction as well as in theory and computational methods have greatly promoted the development of powder diffraction, which is currently adopted in several scientific and technological fields. Therefore the topics of the school span from the fundamental principles of powder diffraction to advanced methods of data collection and analysis with examples of applications of scientific and industrial interests. For each topic, theory will be strictly followed by practical sessions centred on the relevant software so that participants familiarize with some widely used computer programs for data analysis and interpretation of the results. The school is mainly addressed to PhDs and young researchers working in the field of materials science, chemistry, physics, life sciences, earth sciences, cultural heritage and engineering.