Hydration of cement initiates immediately upon contact between water and anhydrous clinker phases, triggering a series of dissolution–precipitation reactions that progressively transform the fluid suspension into a solid, load-bearing microstructure. During this process, the initially free water within the system is continuously redistributed: a portion becomes chemically bound within hydration products, another fraction is physically retained within gel pores and interlayer spaces, while the remaining water occupies capillary pores. This evolving water balance governs not only the development of the solid skeleton but also the onset and progression of shrinkage phenomena in hydrating cement paste. Shrinkage onsets with the setting of the cement paste, as the solid skeleton begins to sustain internal stresses arising from moisture redistribution during self-desiccation. The reduction of free water due to chemical consumption lowers the internal relative humidity of the cement paste, resulting in capillary stresses within the pore network. Thus, the partitioning of water between chemically bound, physically adsorbed, and capillary states becomes a key parameter linking hydration kinetics to macroscopic deformation. Thermodynamics provides quantitative predictions of phase assemblage evolution and chemically bound water content as a function of time, which can be used to estimate the chemical shrinkage arising from differences in molar volumes between reactants and hydration products. This approach allows the chemical shrinkage to be isolated from the total measured shrinkage, thereby enabling the evaluation of autogenous shrinkage. The latter can then be related to internal relative humidity evolution and water distribution with the help of pore-partitioning models, providing insights into the impact of water balance on shrinkage