This book offers a systemic introduction and summarization of nanoscale characterization techniques on cementitious materials. Cementitious composites are ubiquitous in the realm of construction, serving as the backbone of infrastructure worldwide. These materials, typically composed of cement, aggregates, and water, exhibit a complex interplay of mechanical, chemical, and physical properties. In the introductory chapter, we delve into the fundamental aspects of cementitious composites, exploring their composition, structure, and significance in the construction industry. In the second chapter, we introduced the advancements and applications of nano-characterization techniques for cementitious materials including nanoindentation, nanoscratch, modulus mapping, atomic force microscopy-based nanomechanical mapping techniques. Therefore, in the third chapter, the cementitious materials sample surface processing procedure was introduced. In the fourth chapter, nanoindentation, modulus mapping and PeakForce quantitative nanomechanical mapping (PeakForce QNM) test results were comparatively analysed. In chapter five and six, the nanoscale mechanical properties of sodium aluminosilicate hydrate (N-A-S-H) gel in geopolymer paste with and without nanoparticles was evaluated by grid nanoindentation tests. The nano/micromechanical properties of interfacial transition zones in ordinary concrete, recycled aggregate concrete and geopolymer concrete were investigated in chapter seven, eight and nine. Modelled aggregate samples were used to improve efficiency and reduce unnecessary workload in the microscopic characterization. Finally, challenges and future directions were discussed in chapter ten from cementitious sample surface preparation methods, microscopic characterization method for cementitious materials and testing strategies for complicated interfacial transition zones.