It’s getting cold out there! And while winter temperatures may have us yearning for a warm spot by the fireside, cold is a good thing for cell and gene therapies—in many cases, the colder the better. Logistics dictate that international shipping of cellular therapeutics often means freezing them first. Cryopreservation protects fragile cellular material from loss of viability or functionality during transit and storage, by halting chemical and biological degradation processes. To understand how important that is, it is worth noting that two of the hottest cell therapy drugs on the market this year (Yescarta® and Kymriah®) are both cryopreserved prior to infusion into the patient. But how cold does it really need to be to protect the efficacy of these cellular therapeutics? We decided to put that question into perspective.