**3. Flow cytometer (FCM)**

Despite of the advanced technologies superior to the conventional microscopic systems, imaging methods are still not suitable for high-throughput or rapid detection. Therefore, scientists are committed to developing simple, sensitive and high-throughput exosome detection methods. Inspired by single cell technologies, flow cytometer attracted interests of scientists for multiplex large-scale single EV characterization. However, it is difficult to detect particles below 500 nm in size with the conventional FCM. Two approaches could be applied to overcome the problem. First, recognition of proteins on the single EVs was followed by a signal amplification step that could produce detectable structures through FCM. Second, the FCM were customized and optimized for detection in nanoscale.
