Abstract: Future implantable biomedical systems will require power and data telemetry with multiferroic interfaces, signal modulation, low-impedance electrodes with high current injection, remateable connectors - all in a highly miniaturized form-factor with reliability in a reactive aqueous environment. They provide a combination of functions such as neural recording and stimulation, imaging, spectroscopy, electrochemical sensing and others. They, thus, drive the most advanced heterogeneous integration. Advancing system components and their 3D connectivity in small form-factors are both critical to realize such future medical implants. The system components are advanced through innovative nanomaterials, multiphysics-based material designs to achieve the performance metrics, and hybrid additive and semi-additive manufacturing technologies. The integration technologies rely on advanced chiplet fan-out embedding technologies in flexible or rigid-flex substrates that provide seamless but reliable interconnect technologies between the system components. This article will briefly review some of the key functional packaging build blocks towards these heterogeneous 3D implanted medical systems.