These electrode arrays are typically arranged as 32, 36 and 64 grids for recording electrical signals. Obtained signals will be amplified by a filter amplifier and sent to a data acquisition computer. MappingLab offers microelectrodes with different sizes to match the size of samples. They are applicable to record electrical activation and excitation of perfused cardiac tissues in chamber or a whole heart from mouse, rat, Guinea pig, rabbit, sheep and dog in vivo and ex vivo. It can be stably mounted on the ball-joint holder to probe the samples from multiple angles. They are suitable to measure direction and velocity of conduction system as well as to monitor electrical activities from cultured pacing tissues. More excitedly, they can be used in drug testing and safety.