For the fundamental research on metrology and the development of communication technology, link- and system-level simulations provide opportunities to test hypotheses, explore new designs, and assess modifications of systems under development or under test. Realistic simulations can provide insights in channel characteristics while limiting the need for extensive and time-consuming measurement campaigns and provide channel models for further analysis. Link-level simulations allow for testing the performance of a system under different circumstances and scenarios that might be difficult to recreate, e.g., due to safety concerns or rare weather conditions. System-level simulations can provide an insight into network effects and interactions between components while protecting the physical hardware. In essence, findings from link- and system-level simulations pave the way toward successful digital twinning which describes the creation of a virtual replica of a physical system or a process. Through data integration and advanced algorithms, digital twins mimic real-world behavior providing insights into performance, maintenance, and potential failures. By offering possibilities for analysis, prediction, and optimization without impacting their real-world counterparts, digital twins enable safe and cost-effective research and experimentation.