Very high TEM of a section of a stage 2, 4-cell embryo in vivo, (original magnification x50,000). Notice blebbing (Bl) of the outer layer of the nuclear membrane towards the cytoplasm. Two or more vesicles are present within each bleb. Notice the condensed area (arrow) at the site of contact of a vesicle with the inner layer of the nuclear membrane.
N = nucleus
From: Pereda and Croxatto, 1992. Reproduced with permission of the Annals, Academy of Medicine, Singapore.
Source: The Virtual Human Embryo.