ACROPOLIS aims to contribute to the sustainable energy landscape by leveraging advanced digital solutions for real-time simulation, resource flexibility, and collaborative partnerships. The project focuses on digitalized Control and Operation for emerging power systems, using real-time digital simulation tools to accelerate the development, deployment, and market adoption of innovations critical to the 4D energy transition—Decarbonization, Digitalization, Decentralization, and Democratization. At its core, ACROPOLIS is built on three key pillars:  Enhancing the grid integration of renewable energy sources (RES) to support a more sustainable energy mix.  Improving system controllability, reliability, and efficiency through advanced digital control frameworks.  Fostering microgrids and energy communities by promoting collaborative partnerships and innovative technologies. To achieve its goals, ACROPOLIS will develop and validate a suite of Key Exploitable Results, integrating hybrid optimal control tools, digital twins, and Hardware-in-the-loop (HIL) & Power-Hardware-in-the-loop (PHIL) experiments. These innovations will enhance technology performance, extend the lifespan of RES assets, and unlock new flexibility solutions for emerging low-inertia power grids. Ultimately, ACROPOLIS contributes to the transition towards zero-emission power systems, reinforcing Europe's leadership in sustainable energy.