Most high throughput, high content screening and profiling assays rely on exogenous gene expression of reporter genes, fusion proteins and artificially engineered proteins or overexpression of a target of interest. While stable cell lines are a convenient tool for producing the large number of cells required to perform a single screen, they are time-, labor- and cost-intensive to create. Transient transfection offers the ability to quickly develop working assays, however, many of these technologies have limitations on compatible cell types. Additionally, they can require multiple small-scale transfections or use costly transfection reagents to produce a large number of cells. MaxCyte® scalable electroporation offers a cost-effective, reproducible transfection of up to billions of cells in less than 30 minutes with broad cell type compatibility. In this poster we present the transient transfection of a variety of difficult-to-transfect cells and their use in downstream assays. Specifically, we demonstrate how large-scale electroporation of Jurkat, CHO, human skeletal muscle cells and primary neuronal cells produces large numbers of quality transfected cells and can ease the burden of stable cell line engineering.