Cryopreservation could be executed as oocyte cryopreservation prior to fertilisation, or as embryo cryopreservation following fertilisation. Through early blastocyst enhancement, fluid begins to fill embryo. The embryo starts to expand like a balloon. To implant, the embryo need to escape with the shell surrounding it. This is known as "hatching." https://bookmarklayer.com/story18452696/details-fiction-and-ivf