The 6 µm PeakFlow™ Carmine flow cytometry reference beads are stained with fluorescent dyes that have been carefully selected to produce emission peaks coincident with labeled cells used in typical flow cytometry applications. The emission profiles for these standards are intentionally narrow. Because PeakFlow™ beads are highly uniform with respect to both size and fluorescence intensity, and because they approximate the size, emission wavelength and intensity of many biological samples, they can be used to calibrate a flow cytometer's laser source, optics, stream flow and cell sorting system without wasting valuable and sensitive experimental material.