HA21 is a medium magnfication EM view of the large Golgi in a secretory cell. This image and HA22 show the elements of the Golgi Complex: sacs of flattened membranes that are stacked in a cup-shaped fashion and vesicles (v) of various sizes. The darkly staining structures (HA21) are vesicles that contain condensed secretory product. RER and a portion of a euchromatic nucleus (N) can also be seen in HA21.