Individual submicron-sized particles such as bacteria, viruses, cellular organelles and extracellular vesicles can be detected by flow cytometry based on the particle’s light scatter, fluorescence or both. In order to detect individual submicron particles, the flow cytometer requires ultra-clean fluidics and an optimal sample flow rate. This figure shows a histogram (blue) generated from Human Immunodeficiency Virus detect by side scatter alone on a Partec CyFlow Space overlayed with a histogram from sample fluid (gray).