The formation of hydrates in dispersions of cubic tricalcium aluminate (C(3)A)-calcium hydroxide-gypsum was observed using soft X-ray transmission microscopy. This technique allows the continuous imaging of the hydration process without the introduction of drying artifacts. Within minutes, microcrystalline hydrates covered the C(3)A particles but over time large prismatic ettringite crystals are precipitated suppressing the microcrystalline hydrates. Within the resolution of the technique, no protective hydrated layer on the surface of C(3)A particles was observed.