Cryoprotectant
A chemical component of a freezing solution used in cryopreservation (the process of cooling and storing cells, tissues, or organs at very low temperatures to maintain viability).
The purpose of the cryoprotectant is to help protect what is being frozen from freeze damage.
In Greek 'kryos' = cold.
The chemical glycerol, for example, is commonly used as a cryoprotectant to protect frozen red blood cells