Very high power TEM of part of a blastomere of a stage 2, 4-cell embryo in vivo (original magnification x40,000). Shown is a nucleolus (Nl) with a very dense core and an irregular granular periphery (arrows).
From: Pereda and Croxatto, 1992. Reproduced with permission of the Annals, Academy of Medicine, Singapore.
Keywords: blastomere, four-cell embryo, nucleolus, stage 2 embryo
Source: The Virtual Human Embryo.