10 (of 11)
Human embryos developing in vitro. The photos show a fertilized egg, 8-cell stage, cell adhesion,
a compacted morula, a blastocyst and zona hatching.
Photo: Wikipedia (http://en.wikipedia.org/wiki/File:Early_human_embryos.png)
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11 (of 11)
A light micrograph image showing the encounter between sperm and ovum during in vivo fertilization. A single sperm is seen in centre of the image approaching the circular oocyte. Other competing sperm and cells encompass the corona radiata, which forms a protective halo around the central oocyte, are visible at bottom.