Substitutional heterovalent doping represents an effective method to control the optical and electronic properties of nanocrystals (NCs). Highly mono-disperse II-VI NCs with deep substitutional dopants are presented. The NCs exhibit stable, dominant, and strong dopant fluorescence, and control over n- and p-type electronic impurities is achieved. Large-scale, bottom-up super-lattices of the NCs will speed up their application in electronic devices.