Perfect nanocrystals exhibit a variety of highly symmetric polyhedral shapes and have fascinated artists and scientists. Better understanding of nanocrystal growth habits and systematic controlling of their shapes/surface structures are very important for uncovering many shape-dependent physical and chemical properties, especially catalytic performance. Systematic manipulation of nanocrystal shapes is prerequisite for revealing their shape-dependent physical and chemical properties. However, there is no report so far involving shape evolution among high-index faceted nanocrystals, which is critical for understanding their formation mechanism, so as to rationally engineer nanocrystals with desirable surface structures and exceptional properties. The iChEM Prof. Shi-Gang Sun’s group recently reported a successful synthesis of convex HOH Pt nanocrystals enclosed by 48 {15 5 3} facets for the first time by an electrochemical square-wave-potential (SWP) method. This shape is the last crystal single form that had not been achieved previously for face-centered-cubic (fcc) metals. They further realized the shape evolution of Pt nanocrystals with high-index facets from tetrahexahedron (THH) to the HOH, and finally to trapezohedron (TPH) by increasing either the upper (EU) or lower potential (EL). The as-prepared Pt micro/nanocrystals with controllable high-index facets could serve as a promising model for studying single particle behaviors, although they are not suitable for practical catalytic applications because of the large particle size. This study provides a new insight into shape-controlled synthesis of Pt nanocrystals with high-index facets and their formation mechanism. (J. Am. Chem. Soc., 2013, 135, 18754-18757）