For various reasons, microscopic particles (1-100 µm) can form in protein, nucleic-acid or cell-based medicines. Such particles (such as aggregated proteins) can be very dangerous and, among other things, provoke very severe immunological side reactions in patients. Therefore, the design and development of biopharmaceuticals require careful analysis/understanding of the origin of these particles. Flow imaging microscopy (FIM) is an essential technique for this. Unlike other microscopes, FIM is equipped with a high-speed camera and a flow-through cell that allows the automated analysis of particles in representative sample volumes (50-1000 µL). FIM is fundamental equipment for any biopharmaceutical laboratory, but it can also be used to analyze other liquids for the presence of microscopic particles.