File:E2198 contactb.png

Varicose contacts (a,b) are synapses, as demonstrated by the presence of vesicles (b) in a conventionally stained dataset. Incidental contacts (c,d) are not synapses, as demonstrated by the absence of vesicles (d) in a conventionally stained dataset. Owing to its high resolution, EM reveals when a thin glial sheet is interposed between two neurons (e), a situation that would appear to be a contact point between the two neurons in a light microscopic image.