Many of the biggest barriers to cost-effective sustainable fashion often emerge far upstream in the supply chain, long before fabrics reach designers or manufacturers. Critical challenges include developing agricultural waste valorization methods for alternative fibers and cultivating feedstocks for breakthrough biofabrication of new materials. This panel explores the obstacles and solutions for innovating raw material sourcing — bottlenecks that remain largely unknown or misunderstood by the wider fashion industry, discussing how to bridge the gap between cutting-edge materials innovation and commercial viability to reach scale.