Cryo-storage bag, a sterile container used for storing tissue prior to freezing in a tissue bank. Parts of the heart taken from a donor or heart transplant recipient can be used in the treatment of other patients. The heart is dissected and its aortic, pulmonary and mitral valves as well as some other tissues and conduit sections are removed. The extracted tissue is then treated in antibiotic solution before being cooled and stored in the vapour phase of liquid nitrogen, a procedure known as cryopreservation. Small samples are tested for disease and if the tissue passes, it is stored until matched with an appropriate patient.