Fig. 4From: Methods to analyze extracellular vesicles at single particle levelThree types of electron microscopy (EM) techniques. a Scanning electron microscopy (SEM) detects backscattered electrons (BSE) or secondary electron (SE) signals of EVs deposited with metal film. b Transmission electron microscopy (TEM) acquires an image by detecting the electrons transmitted through the negatively stained EVs with heavy metal according to the electron transmittance. c The principle of cryo-TEM is similar to that of TEM, but it freezes EVs to rapidly fix them to maintain their natural spherical shapeBack to article page