An environmentally harmless method of synthesizing extremely small CdSe and highly luminescent CdSe/CdS core-shell quantum dots (see Figure) with CdSe cores of 1.2-1.5 run diameter is reported. The CdSe/CdS core-shell quantum dots exhibit 60-80% quantum yield at room temperature. The emission peak is tunable from 445 to 517 nm (purplish blue to green yellow) by increasing the diameter of the CdSe core and/or the thickness of the US shell.