For generations, materials scientists have sought to coax two-dimensional MXene nanosheets into fibers worthy of their individual promise, only to find the edges where sheets meet remain stubbornly weak. A research team has now answered this ancient problem of connection with an idea borrowed from medieval armorsmiths: threading molecular cords — carbon nanotubes wrapped in cellulose — between the sheets to bind them as leather laces once bound layered metal plates. The result is a fiber that is dramatically stronger, tougher, and more ductile than before, yet loses none of the electrical cond