We present an interactive platform that enables human users to interface with microbiological living cells through a touch-screen, thereby generating a tangible interactive experience with the microscopic world that is hidden to most people. Euglena gracilis, single-celled phototactic microorganisms, are imaged and optically stimulated via a microscope setup equipped with a projector and a touchscreen display. Users can directly interact with these organisms by drawing patterns onto the screen, which displays the real-time magnified view of the microfluidic chamber with the motile euglena cells. The drawings are directly projected onto the chamber, thereby influencing the swimming motion of the cells. We discuss the architecture of the system and provide exploratory user testing results in a facilitated setting, which shows engaging nature of our system for children and the general public. In conclusion, our tangible interactive microscope allows artistic expression and scientific exploration with the ease of "child's play".