Studying single cells reveals biology that cannot be explored using bulk techniques. Cell sorters provide the opportunity of separating single cells either for cell culture or for downstream molecular studies such as qPCR to study specific gene expression and single cell mRNA sequencing. Some of these molecular studies can be very expensive so the investigator will often want reassurance that the cell sorter can reliably deposit a single droplet into each well of a 96-well or 384 well plate. Such plates can sometimes have a very small volume of fluid as reducing the volume of fluid can reduce the cost of the assay. To miss some of the wells could leave the data set incomplete requiring costly repetition. To verify this by microscopy is at best very time consuming and at worst impossible.

Here, we describe an inexpensive method of verifying whether a well in either a 96 or 384-well plate did receive a sorted droplet from a cell sorter into the fluid at the bottom of the well. The method requires no special equipment or expertise and is rapid enough to be performed directly before the single cell sorting experiment.