After the completion of the equilibration step,
oocytes are then placed in vitrification medium
which is a solution having higher strength of
cryoprotectants. The exposure time of oocytes in
the vitrification medium is very short, approx
60 s. This is followed by oocyte loading on cryotec (filmstrip), a carrier device, and direct plunging in liquid nitrogen. To ensure maximum
cooling rate (23,000 °C/min), cryotec should be
submerged in liquid nitrogen with continuous
vertical movements. Cryotec is then covered with
the cap still under liquid nitrogen. This helps in
avoiding mechanical damage during storage