What appear to be large, shiny coffee beans are in fact food-grade stainless steel shells filled with a food-safe phase change material (PCM). The PCM is a solid at room temperature, but when you drop the Joulies into a hot beverage, the PCM liquifies and begins absorbing heat, cooling your joe to a comfortable drinking temperature. On the other end, when your drink begins to get cool, the PCM begins to re-solidify and releases the heat it has stored, thus keeping your drink warm. Ultimately, the Joulies extend the window of time during which your hot drink is drinkable.
Source: the-gadgeteer.comAdded: 8 April 2011