To further advance the scientific understanding of the intricate electrical activities in the heart, which are of vital importance for the human body, more elaborate mathematical modeling is needed with the support of supercomputing. In this project, we propose to implement and optimize a new simulator of cardiac electrophysiology, based on the latest cellresolved modeling approach. The expected level of physiological details and the resulting computational resolution can only be achieved by an effective use of modern supercomputers. By combining efficient numerical algorithms with hardware-compatible software implementations, we want to enable computational scientists to carry out novel “in-silico” experiments. Moreover, this project will consolidate the existing expertise of the project partners on large-scale simulations using realistic geometries and unstructured meshes, optimized parallel programming and use of nonx86 architecture (A64FX processors) and accelerator (Nvidia GPUs).