This chapter describes the most recent advances made in the use of functional cyclic organic carbonates in synthetic chemistry and polymer development. In particular, the type of carbonate, its functionalization and its ring size will be discussed and highlighted in detail. Cyclic carbonates are amenable to various types of ring-opening chemistry which allows to use them as precursors toward fine-chemical, advanced intermediates and monomers for poly-carbonate and poly-urethane synthesis. The synthetic concepts and their mechanistic intricacies are presented to provide a detailed context from their conception to their utilization as a means to mark the current achievements but also their limitations. Future directions are identified that will hopefully spur new advancements while enforcing a prominent position of these CO₂-based heterocyclic structures in various areas of modern science and sustainable progress.