A system for monitoring cell-substrate impedance of excitable cells and monitoring the beating cycle of cardiomyocytes, the system including: a device for monitoring cell-substrate impedance at 20 millisecond time resolution, the device having one or more wells on a nonconductive substrate, wherein at least one well of the one or more wells comprises an electrode array fabricated on the substrate for measurement of cell-substrate impedance at 20 millisecond time resolution; an impedance analyzer that measures cell-substrate impedance from the at least one well at 20 millisecond time resolution; electronic circuitry that electrically connects the electrode array from the at least one well to the impedance analyzer; and a software program that analyzes the measured cell-substrate impedance.