Ultrastructure of a cryopreserved human sperm. The cryoprotectant used was glycerol/egg yolk. Ice was nucleated within the straw at -7°C. The sample was then cooled at 10°C per minute to -100°C and then transferred to liquid nitrogen. A cross fracture of the straw followed by deep etching removes ice and reveals a sperm associated with the interface between the freeze concentrated material (non-etched material) and ice crystals. The sperm tail extends into the void previously occupied by ice and has been fractured during sample preparation.
