As more genomes are sequenced, challenge of rapidly unraveling the functions of genes was faced. To that end, cell microarrays have been recently described that permit transfection of thousands of nucleic acids in parallel and enable the analysis of phenotypic consequences of such perturbations. As many parameters can influence the efficiency of transfection and consequently protein expression or extinction, some important features in manufacturing cell microarrays for functional exploration of genomes were described.