Protocols

Abstract

Basically, two types of electron microscopes are used for studying pre-implantation embryos: The scanning electron microscope and the transmission electron microscope. The scanning electron microscope is used for visualisation of cell and tissue surfaces by creating an image from the secondary electrons that are emitted from a thin gold coating of a specimen dried by e.g. critical point drying, when it is hit by a beam of primary electrons. The focus depth of the scanning electron microscope is relatively high and images of an embryo obtained by this technique are rather self explanatory: The embryo appears as a three dimensional spherical structure as a ball viewed by the naked eye. In contrast to its scenic appearance, the scientific information gained by scanning electron microscopy is rather limited. Thus in the following, transmission electron microscopy, which from a scientific point of view is of far greater importance, will be set in focus. At transmission electron microscopy, extremely thin sections of specimens are observed allowing for evaluation of the interior of e.g. the blastomeres of an embryo.