Transmission electron microscopy (TEM) is a powerful analytical technique that allows for the visualization of the microstructural and nanostructural composition of materials at atomic or molecular scales. In the context of cement and concrete, TEM is used to study the fundamental aspects of cement hydration, the formation of hydration products, and the microstructural changes that occur under various environmental conditions. TEM operates by transmitting a beam of electrons through an ultra-thin specimen. Interactions between the electrons and the specimen produce detailed images that reveal the arrangement of atoms and the presence of phases and defects that are not visible through other microscopic techniques. This detailed level of analysis is crucial for understanding how different environmental conditions, such as exposure to sulfates, chlorides, and extreme temperatures, affect the internal structure of cementitious materials (Scrivener et al. 2004).