There's a special active heating garment that instantly warms your body without any involvement of batteries or insulators. Apparently, the Entropy vest can change its state of matter to give heat to the wearer.
It might appear as something that you can only see in sci-fi films or video games, but it's really available in real life. It has a liquid phase-change material to keep you warm in extremely cold conditions.
According to Fast Company, the Entropy vest is a one-of-a-kind garment that you can wear to stabilize heat inside your body. It contains a cyan gel that is capable of heating you up for up to 104 degrees Fahrenheit.
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