Flow cytometry fluorescence in protein research. Depiction of yeast cells that have been labelled with fluorescent beads to allow them to be assessed using flow cytometry methods. Flow cytometry is a laboratory technique used to measure and count cells. Here, it is being used to assess the viability and nature of fungal yeast cells. This technique is used in protein research to differentiate between different proteins, and also to study diseases caused by misfolded proteins known as prions.