Increased stress tolerance viability and viable biological material

using hydrostatic pressure to enhance the viability of viable biological material intended for cryopreservation, wherein said biological material is an oocyte of a vertebrate animal comprising: (a) applying a hydrostatic pressure in the range of 10 to 100 MPa to said biological material; (B) maintaining said viable biological material at the hydrostatic pressure for a period of from 10 seconds to 150 minutes; (C) releasing the hydrostatic pressure; with the proviso that said viable biological material is non-human.