Exosomes are found in many types of body fluid and can be isolated by a variety of methods such as ultracentrifugation, size-exclusion columns (SEC) and marker based pull-down assays (commercial kits). Isolated exosomes are characterized by a combination of techniques including staining for exosome-specific protein markers (using immunoblotting), nanoparticle tracking analysis (NTA), and electron microscopy (EM). These techniques have been widely applied to evaluate the quality and concentration of isolated exosomes. Of note, the methods for exosome isolation, purification and characterization are developing rapidly as insights are gained into the biological features of exosomes. CSF, cerebrospinal fluid.