Example EM images . (A and B) A comparison of images of ultrathin sections stained for glycogen (A) or not (B). The stained image shows granules of 15–40 nm (enlarged in inset). The corresponding unstained image, of a section cut from the same block, shows roughly circular clear areas separating thin myofilaments, consistent with unstained granules. The image in A also shows a thick deposition of staining on SR and junctional T tubule membranes, not present in B.