Novel circle-on-line microelectrode arrays based-on electronic impedance measurement, are fabricated either on glass slides or micro-porous membrane and integrated into the wells of ACEA 96X microtiter E-Plates or 16X RT-CIM™ devices. Electronic impedance of the microelectrodes is mainly determined by the ionic environment in the regions around the electrodes and can be monitored as a baseline impedance by applying an electrical field to the electrodes. The presence of the cells will affect the local ionic environment at the electrode/solution interface, leading to an increase in the electrode impedance. The more cells are on the electrodes, the larger the increases in electrode impedance. In addition, the impedance change depends on the quality of the cell interaction with the electrodes. For example, increased cell adhesion or spreading will lead to a larger change in electrode impedance. Thus, electrode impedance, which is displayed as cell index (CI) values, can be used to monitor cell viability, number, morphology, and adhesion degree in a number of cell-based assays.