Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for light emitting applications,but suffering from the low photoluminescence quantum yields at low excitation fluencies.[1-3] Recently,we developed a ligand-assisted reprecipitation(LARP)strategy to fabricate CH3NH3PbX3(X=Br,I,Cl)nanocrystals.[4] By controlling their size and shape,we demonstrated the size-and shape-dependent photoluminescence properties.