Once multicellularity was thriving, a key development involved the emergence of epithelial layers that separated “inside” from “outside”. Most epithelia then generate their own transepithelial electrical signals. So electrical forces were instrumental in the development of epithelial tissues, which themselves generate further electrical signals. Epithelia also developed extracellular basement membranes which act as spatially diverse scaffolds to organize multiple molecular interactions, dependent on electrical forces. Epithelia and basement membranes were constructed using electrical forces and their evolution had electrophysiological consequences.