As the extension, so the twist Artificial internal structures blur the boundary between materials and machines

More than 350 years ago, Robert Hooke wrote, “As the extension, so the force,” when he appreciated how solids deform. This law of linear elasticity applies to all materials and as such constitutes the foundation of solid mechanics. On page 1072 of this issue, Frenzel et al. (1) created and investigated a metamaterial—artificially architected materials designed to exhibit on-demand effective properties surpassing that of their constituents—that turns Hooke's statement on its head. Extension (or compression) of this material also leads to its undergoing a twisting motion, a response closer to that of a machine.