A system for monitoring cells, which includes a device for monitoring cell-substrate impedance, the device having a plurality of wells on a nonconductive substrate, where each of the plurality of wells has an electrode array fabricated on the substrate for measurement of cell-substrate impedance; an impedance analyzer that measures cell-substrate impedance from the plurality of wells; electronic circuitry with multiple analogue-to-digital conversion channels, where the electronic circuitry electrically connects the electrode arrays to the impedance analyzer such that the electrode arrays are electrically monitored at millisecond time resolution; and a software program that analyzes the measured cell-substrate impedance.