Drop-seq is a technology we developed to enable biologists to analyze RNA expression genome-wide in thousands of individual cells at once. We first described this in a 2015 paper in Cell. Though commercial implementations of droplet-based single-cell RNA-seq also now exist, we have made Drop-seq open-source and want to make sure that any lab can build their own system. The materials for constructing a Drop-seq setup in one’s own lab can be obtained for about $6,000. The reagents for performing Drop-seq cost about 6 cents per cell.This is a supplemental protocol of our Drop-Seq Protocol for measuring droplet volume in home-made microfluidic devices.