The adoption of novel materials and device structures will be necessary to overcome the limitations of existing memory technologies in future low energy applications. One alternative that has risen to prominence is "resistive memory: or "R(e)RAM", in which information is represented by two or more resistance states. In one particularly promising approach to this type of memory, resistance is controlled by the movement of ions coupled with electrochemical (redox) processes. In the case of cation-based devices, a solid electrolyte is placed between inert and oxidizable electrodes to enable a metal ion current to flow. This ionic current feeds a reduction reaction, resulting in the formation of a metallic bridge within the electrolyte. Since the volume of the bridge depends on the total number of metal ions that are reduced, the device resistance can be controlled by programming current and time, which means that it is possible to create multiple discrete resistances levels to represent more than one binary digit per cell. In addition, it is feasible to layer such memory cells above the substrate in passive diode-isolated arrays to further increase information storage density or provide integration flexibility. This presentation will discuss the materials and operational characteristics of cation-based resistive memory and will demonstrate, by way of examples from academia and industry, why this technology has already reached the point of commercialization.