Vitrification has become an important alternative to standard slow programmable freezing methods for cryopreservation of primate ES cell lines including Human iPS cells because of the higher survival rates of cells after thawing. However, the vitrification requires an ultra-rapid freezing protocol, usually less than 15 seconds between making cell suspensions and freezing in liquid nitrogen. Cell Reservoir One (Vitrify) is a novel serum-free cell culture freezing medium for vitrification method, which contains a water-soluble glycoprotein SERICIN isolated from the silkworm cocoon as a major constituent. It provides high survival rates of primate cells, such as Monkey ES cells and Human iPS cells even with a longer freezing protocol;up to 60 second from the cell collection to freezing in liquid nitrogen. *Cell Reservoir One (Vitrify) is produced in corporation with SEIREN. (Patent pending)» High viability with a longer freezing protocol (up to 60 seconds)» Low toxicity to cells (DMSO and acetamide free)