Using a simple physical model, researchers at the University of Osaka, The National Institute of Advanced Industrial Science and Technology (AIST), RIKEN, and the Institute of Science Tokyo revealed how superionic conduction emerges when mobile ions undergo sublattice melting while the surrounding crystal framework remains intact. Near this transition, ions move cooperatively in spatially heterogeneous, string-like patterns, aided by anharmonic lattice motion. The findings identify general physical principles connecting lattice softness and collective transport, potentially guiding more efficient development of solid electrolytes for batteries and energy-conversion technologies.