An oocyte vitrification carrier is a small, specialised device used to hold an egg (or embryo) during the ultrarapid cooling process of vitrification. The carrier is designed to hold the smallest possible sample volume, because volume is the primary determinant of cooling rate. Faster cooling means the intracellular water vitrifies (forms an amorphous glass-like state) rather than forming damaging ice crystals. Carriers are generally categorised as open (faster cooling, some contamination risk) or closed (contamination-protected, slightly slower cooling). Choice depends on your lab’s validated protocols and applicable regulatory requirements.