Solid state NMR was used to obtain data on the atomic level structure of calcium silicate hydrate (C-S-H) that formed from a variety of starting materials under a variety of conditions. Because C-S-H is the major component of hydrated portland cement, a knowledge of its structure and of its structural evolution will ultimately allow users of cement containing materials such as mortars and concrete to more accurately predict the physical and mechanical behavior of these materials once they are placed into service. From the outset, the goal of the work was to observe the hydration process on the atomic level, integrate the findings with existing data in the literature, and refine hydration models as necessary to accommodate the newly acquired data.