Abstract: Embodiments described herein can include one or more modular storage units for use with a refrigerator system. The modular storage units can include a door that is movable from a closed position to an open position; a back wall; side walls; and a base. The modular storage unit can have an air inlet disposed in the back wall for receiving chilled air from the refrigeration system. The modular storage unit can include a temperature sensor that detects the temperature within the interior volume and an insulating wall comprising a phase change material disposed within the insulating wall. The modular storage unit can include a locking system configured to lock the door. Multiple modular storage units can be used in one refrigerator system, and each can be removably coupled to an interior storage compartment of the refrigerator system. Embodiments described herein can be integrated into existing refrigeration systems.