In this master thesis, the characterization and the optimization of a miniaturized microscope-integrated bioreactor for mechanical training of engineered cardiac tissues (ECT) is presented. The bioreactor design was conceived to be characterized by a miniaturized and modular architecture to allow meso-scale cardiac tissue culturing and training, and in order to guarantee the ease of microscopy monitoring and analysis. The physical characterization of the main device’s modules of functioning has concerned (i)the system implemented to apply mechanical stimulation to the heart tissue and (ii)the system exploited to functionalize the ECT and to analyse the biological response of it. The optimization of the design has permitted to combine quasi-static and dynamic contraction on the cardiac tissue, as well as its electrical parameters evaluation.