A mains electricity (AC-powered) device designed to keep temperatures in a container between pre-established limits well below the freezing point of water [i.e., cryogenic temperatures, below -130? Celcius (-202? Fahrenheit)]; typically from -150? to -200? Celsius (-238? to -328? Fahrenheit). The device usually includes temperature sensors, thermometers, a display, connecting cables, and sometimes microprocessors and alarms. It is mainly used in healthcare facilities for containers used for preservation of biological tissues (e.g., embryos, bone), in cryosurgical units, and in blood bank cryogenic freezers (e.g., to store red blood cells).