Controlling the nanocrystal shape may initially seem like a scientific curiosity, but its goal goes far beyond aesthetic appeal. For metal nanocrystals, shape not only determines their intrinsic chemical, plasmonic, and catalytic properties but also their relevance for electronic, optical, and sensing applications. Part of my research in the last five years has focused on shape-controlled synthesis of noble metal nanocrystals. While the synthetic methodology mainly involves solution-phase redox chemistry, we have been working diligently to understand the complex physics behind the simple chemistry – that is, the nucleation and growth mechanism leading to the formation of nanocrystals with a specific shape. Polyol synthesis of silver nanocrystals provides a good example to illustrate this concept. We discovered that the shape of a nanocrystal are dictated by both the crystallinity and shape of nanocrystallite seeds, which are, in turn, controlled by factors such as reduction rate, oxidative etching, and surface capping. The same mechanism also works for other systems including gold, palladium, and platinum. The success of these syntheses has enabled us to tailor the electronic, plasmonic, and catalytic properties of noble metal nanocrystals.