REDstack owes its name to the RED technology, and its practical implementation with the systems it builds using stacks of membranes, namely RED stacks. A membrane stack contains many hundreds of cell pairs, increasing the total stack voltage with every additional cell pair. Each cell pair contains two different types of ion-exchange membranes: a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM), with thin spacers used to keep the membranes from touching and allow water to pass between them. There is a driving force on the dissolved salt ions to diffuse through the membranes into the fresh water compartments. The positively charged ions (e.g. Sodium, Na+) can pass through the CEM, and the negatively charged ions (e.g. Chloride, Cl-) can pass through the AEM. The opposing transport of the positive ions to one side of the stack and negative ions to the other side of the stack is converted into electricity at the electrodes.