Eight-cell embryo. Coloured scanning electron micrograph (SEM) of an 8-cell human embryo, three days old. It is drilled open to biopsy the embryo to test its genes for inherited diseases. The embryo is ontop of a pin (grey, at bottom). It is surrounded by a thick zona pellucida (brown) protective layer into which a window has been drilled. Large cells of the embryo are seen inside (coloured) while smaller spherical structures will degenerate. Embryo cells are called blastomeres & the embryo is termed a morula. It has yet to im- plant in the womb. By removing one or two blasto- meres, genes of the embryo can be examined. Magnification: x570 at 5x7cm size. x2,000 at 8x10"~LANDSCAPE"