"dealii-X: an Exascale Framework for Digital Twins of the Human Body" is a pioneering project aimed at developing a scalable, high-performance computational platform using the deal.II library to create accurate digital twins of human organs, with emphasis on the human brain. This framework will leverage exascale computing capabilities and existing lighthouse applications to simulate complex biological processes in real-time, aiding in personalized medicine and advancing the diagnosis and treatment strategies of neurological disorders. The computational complexity to solve the underlying mathematical models has previously prevented the simulation knowledge from being translated into clinical practice. By integrating cutting-edge HPC technologies with multiphysics and multidisciplinary approaches, dealii-X will deliver unprecedented computational efficiency and fidelity in biological modeling. The project represents a significant leap toward the future of medical diagnostics and treatment planning, offering a robust tool for researchers and clinicians alike.