We have constructed a reusable flow cell in which the aggregation of cells in low-attachment microwells to form spheroids can be monitored in real-time using electrical impedance. Culture in dynamic flow conditions allows media to be refreshed without disturbing the cells. The use of transparent ITO electrodes for sensing, and the methods used for fabrication of porous membrane microwells, allow the spheroids to be observed using a microscope. Electrodes for addressable measurement of individual microwells have also been developed