Freeze fracture electron microscopy of a mouse oocyte cryopreserved in a straw (0.25ml capacity). The cryoprotectant used was dimethylsulphoxide (1.5M) + serum (10%). Ice was nucleated within the straws at -7°C. The sample was then cooled at 0.3°C per minute to -60°C and then transferred to liquid nitrogen. A cross fracture of the straw followed by deep etching reveals a highly shrunken oocyte, which has shrunken in a non spherical manner.