Exosomes are released by cells as self-contained vesicles with an intact lipid 
bilayer that encapsulates a small portion of the parent cell. Exosomes have been 
studied widely as information-rich sources of potential biomarkers that can 
reveal cellular physiology. We suggest that quantification is essential to 
understand basic biological relationships between exosomes and their parent 
cells and hence the underlying interpretation of exosome signals. The number of 
methods for quantifying exosomes has expanded as interest in exosomes has 
increased. However, a consensus on proper quantification has not developed, 
making each study difficult to compare to another. Overcoming this ad hoc 
approach will require widely available standards that have been adequately 
characterized, and multiple comparative studies across platforms. We outline the 
current status of these technical approaches and our view of how they can become 
more coherent. J. Cell. Physiol. 232: 1587-1590, 2017. © 2016 Wiley Periodicals, 
Inc.