For many years, it was thought that passive matrix addressing of electrophoretic image displays (EPIDs) was impossible due to the absence of a threshold. We proved that there are ways to bypass this [Proc. 22nd Int. Display Res. Conf. (2002) 251]. However, the physical basis was not fully understood. This article presents new insights in the physics of EPIDs. By applying the theory of dielectrophoresis (DEP), several discrepancies between theory and measurement, that occurred in explaining properties of EPIDs, are solved. We introduce a new terminology: DEPIDs. For the first time the theory of DEP is applied to model the movement of pigments in electronic paper.