Lattice engineering is an important approach to realize atomic-level surface control over metal nanostructures towards enhanced catalytic performances. However, precise engineering of the lattice of metal nanocrystals to control its crystal phase, surface defects, and lattice strains, particularly via wet-chemical methods, remains a key research challenge.[1,2] This talk will introduce some interesting discoveries we have recently made in engineering the crystal phase and surface defects of metal nanostructures with facet-specific characterizations and property studies.[3-5] The importance of phase dependency in catalysis and beyond will be highlighted. Insights to develop synthetic methodology towards precise lattice engineering will also be discussed.