This lecture covers the principles of Microstructure Characterization by Scanning Electron Microscopy (SEM), explaining how SEM works, the interactions between electrons and matter, and the generation of backscattered electrons, secondary electrons, and characteristic X-rays. It also discusses the morphology study of raw materials, the study of polished cross-section samples, the setting of a good image in the electron microscope, and the microstructure of hydrated samples. Additionally, it delves into EDX analysis, C(-A)-S-H composition, and EDX mapping for phase distribution and damage characterization in cementitious materials.