Scientists transformed common mushrooms (Agaricus bisporus) into a fast-expanding cryogel sponge that stops severe bleeding. Made from natural chitin and glucans, the mushroom sponge absorbed over 15 times its weight in water and expanded in just 2.1 seconds. In rat liver injury models, it outperformed leading commercial products like Celox, triggering rapid clotting while avoiding toxic chemicals and preserving biocompatibility.