A method of maintaining a thermal history (369 699) of samples stored in a temperature-controlled sample storage system is provided. The system can include: one or more containers (218, 220 522) each storing one of the samples one or more storage objects (210-216, 208 510, 516-518, 520 654-660, 662) each housing one or more containers or other storage objects one or more structures (200-206 512 650) defining a temperature-controlled storage environment and housing the one or more storage objects machine readable tags (14) each of which is associated with a separate container and storage object, each tag encoding an identification code and having a temperature-dependant characteristic and an interrogator (12) for reading the identification code and the temperature-dependant characteristic.
