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The ability to straightforwardly deliver engineered nanoparticles into the cell cytosol with high viability will vastly expand the range of biological applications. Nanoparticles could potentially be used as delivery vehicles or as fluorescent sensors to probe the cell. In particular, quantum dots (QDs) may be used to illuminate cytosolic proteins for long-term microscopy studies. Whereas recent advances have been successful in specifically labeling proteins with QDs on the cell membrane, cytosolic delivery of QDs into live cells has remained challenging. In this report, we demonstrate high throughput delivery of QDs into live cell cytoplasm using an uncomplicated microfluidic device while maintaining cell viabilities of 80–90%. We verify that the nanoparticle surface interacts with the cytosolic environment and that the QDs remain nonaggregated so that single QDs can be observed.