Semiconductor quantum dots (QDs) have been called artificial atoms because of their discrete electronic structures. Assembling them into artificial molecules may greatly expand our capability in controlling physical properties on the nanoscale. Here we show the successful assembly and size control of colloidal PbSe QD clusters into large-scale templates defined by block-copolymer patterns. Following the exchange of capping molecules, the QD clusters behave as artificial molecules due to enhanced and local electronic interactions.