Earlier this summer I was sent a new style of cooler inserts to try, made by a company called Arctic Ice. Instead of petroleum goo, Arctic Ice inserts are filled with a biodegradable, plant-based phase-change material (PCM). I barely passed physics (and biology for that matter), but from what I gather, a PCM has the ability to store or release energy, often in the form of heat. According to the company's press materials: "When Arctic Ice approaches its melting point (that's the phase change) it begins absorbing more heat while stubbornly refusing to warm up. It holds a constant, pre-defined temperature (34ºF or 5ºF) until the entire cooler pack finally thaws."