Abstract: The present invention provides a device capable of exhibiting a time-temperature dependence that comprises an upper layer carrying a first reactant selected from a group of materials such as chelating agents and a base layer carrying a second reactant adapted to react with the first reactant upon triggering. A barrier layer is provided between the upper layer and the base layer. Visual characteristic is changed depending on time and temperature after triggering had occurred while the device is not susceptible to environmental conditions and can be stored in room temperature.