Fig. 2 . High power SEM of the same stage 4 embryo in vitro shown in Figure 1 . Measuring bar = 130 µm. The blastocyst is oblong and flattened. The trophoblast cells have bulging surfaces revealing their borders. Those at the apex of the blastocyst exhibit many short microvilli. The blastocyst adheres to a pinopode area on endometrial cells. Flattened endometrial cells predominate the surrounding area. (From: Bentin-Ley et al. 1999. Reproduced with permission of the publisher, Oxford University Press.)