**2. Single EV imaging**

Due to the sub-200 nm diameter of most EVs, conventional optical microscopies are precluded for direct observation or imaging of EVs. Nano-scaled imaging methods which are applicable to the scale of EVs include electron microscopies (EM), atomic force microscopy (AFM), total internal reflection fluorescence microscopy (TIRFM) and stochastic optical reconstruction microscopy (STORM).
