Abstract: An in-situ observation of the initial nucleation ofthe colloidal crystal was performed by utilizing a long working distancemicroscope. The streamlines in the vicinity of the three-phase contact lineare calculated by the fluid dynamics software Fluent. The trajectory of theparticle indicates that the streamline is bent around short chains. Whenthe particle goes close to a short chain, a horizontal flow pushes theparticle to the end of the short chain (flowing-around, FA). The simulationindicates that the particles have the abilityof self-adjusting when they are assembled into a colloidal crystal. The FA wouldinhibit too fast growth in a local area, which would lead to a straightgrowth front. This study provides an insight into theself-assembling dynamics and the nucleation process for colloidalcrystal growth.