To make the revolutionary IBP mug, Klaus Sedlbauer, the head of the Fraunhofer Institute for Building Physics (IBP), and colleague, Herbert Sinnesbichler, used phase change material (PCM), a wax-like substance used in construction to keep rooms cool in summertime.
"If you are drinking hot tea in one of these cups," Sinnesbichler told Der Spiegel magazine, "the drink's heat is directed straight into the still solid PCM. This heat... melts the PCM - kind of like wax - and turns it into a liquid."
Once the material has become liquid, it retains thermal energy without absorbing any more heat, reports The Telegraph.
"Warm drinks - like coffee or tea - are best enjoyed at 58 degrees Celsius," Sedlbauer said.
"In order to reach and maintain this temperature, we fill the mug with a type of PCM that becomes a liquid at exactly 58 degrees Celsius," the expert added.
The material absorbs the heat of the mug's content like a sponge, stores it and brings it down to the optimal temperature. And then the PCM helps maintain the content's temperature at this optimal level by slowly releasing the stored heat back into the mug's contents.
"Under ideal circumstances," Sedlbauer says, "the optimal temperature can be maintained for 20-30 minutes."