Containers are provided. An exemplary container for storing an item comprises: an insulating material; a pressure-maintaining container defining an interior, the pressure-maintaining container being surrounded by the insulating material; and a temperature-maintaining material disposed within the interior of the pressure-maintaining container, the temperature-maintaining material being arranged to maintain a temperature of an item placed with the container. The temperature-maintaining material sublimates during warming to produce sublimation gasses and the pressure-maintaining material is operative to control venting of the sublimation gasses such that pressure higher than atmospheric pressure is maintained about the temperature-maintaining material. Methods also are provided.