© 2019 Elsevier B.V. Recent progress in microengineering has included the demonstration of various micropumps; however, these pumps are typically driven by an external energy sources such as electrical power source. Thus, there is a limitation to the integration of such pumps into microdevices. Here, we report fabrication of the world smallest autonomous hybrid pump powered by cardiomyocytes that self-organize into microtissues bridging PDMS made elastic microstructure. First, it was confirmed that cardiomyocytes formed several contractile bridges crossing the side walls of micro-groove and optimized the conditions under which they formed. Second, an actual ultra-small fluid oscilaltion unit for pumping (200 μm × 200 μm × 150 μm)was fabricated by embedding the micro-piers in a semi-closed microfabricated space filled with physiological buffer and closed with a cover glass lid on the device. Spontaneous and periodical oscillations of both micro-piers and the fluid in the device were confirmed. Simulation to understand the flow pattern and distribution of the flow velocity matches well with the experimental results. The theoretical flow rate assuming the use of ideal check valves was 1.0 nL/min. In the future, we expect this cardiomyocyte-driven device to be applied to applications such as in vivo micropumps, small-scale organs-on-a-chip and large-scale drug discovery assays.