A maturing application of reprogramming and stem cell technologies is their application to understanding how genetic variation that underlies disease risk impinge the function of affected cell types. However, a major limitation of this approach has been the number of patients and genetic variants that can be reasonably analyzed. I will describe a new strategy we have developed that allows us to simultaneously measure phenotypes in cell types derived from as many as 100 individuals in a single tissue culture well. These approaches, we call “Dropulation Genetics” and “Census sequencing” not only have allowed us to probe how genotype underlies phenotype at previously impractical scales, they have also provided a remarkable improvement in sensitivity and assay reproducibility. I will describe practical application of these approaches in psychiatry, neuromuscular disease and susceptibility to infectious agents.