State-of-the-art flame retardant cotton textiles suffer from release of formaldehyde and are uncomfortable to wear. Empa scientists managed to circumvent this problem by creating a physically and chemically independent network of flame retardants inside the fibers. This approach retains the inherently positive properties of cotton fibers, which account for three-quarters of the world’s demand for natural fibers in clothing and home textiles. Cotton is skin-friendly because it can absorb considerable amounts of water and maintain a favorable microclimate on the skin.