Cryopreservation is a process that preserves tumor tissue by cooling the sample to very low temperatures. While it is scientifically possible to revive (or warm) cryopreserved tissue and develop O-PDX models from it, the success of that approach depends greatly on the method of cryopreservation, the size of the tumor tissue sample and its condition. At Certis, we prefer to work with fresh tissue (received and engrafted within 24 hours of biopsy or surgery) to maximize the likelihood of a successful study.