Molecular communication (MC) is an emerging field that aims to establish chemically driven information exchange mechanisms between molecular robots and cells. This technology enables the complete chemical implementation of multicellular molecular systems capable of achieving complicated tasks by coordination, leading to applications such as targeted drug delivery, biocomputing, and tissue engineering. Control theory provides useful concepts and tools that provide insights for better understanding and designing the dynamics of MC systems. In this section, we provide an overview of synthetic MC systems from the perspective of systems and control. Specifically, this section focuses on control-theoretic models and analysis methods for understanding the fundamental characteristics of diffusion-based MC systems.