Our group is turning cellulose nanocrystals — a cheap, sustainable, plant-derived material — into liquid-crystal-based photonic films and fibers that change color under strain. We seek to fabricate "mechanochromic" fibers that are tough, flexible, and can be knotted without breaking, all while shifting color as they stretch. The work points toward new classes of low-cost, biodegradable sensors and structurally colored materials.