Absorbent structures that form superabsorbent polymers in situ. The structures include an absorbent material and a fibrous material containing an activating agent. The fibrous material releases the activating agent upon stimulation with an activator, which causes the polymer to become a superabsorbent polymer. The absorbent component is desirably a water-swellable, water-insoluble polymer. The absorbent structures form a superabsorbent composition in situ. Methods of making the activating agent containing fibrous material are provided.