The paper discusses the evolution of synchronous languages over the past 12 years, highlighting their advancements, challenges, and successes. Synchronous languages, such as Esterel, Lustre, and Signal, have become a key technology for modeling, specifying, validating, and implementing real-time embedded systems. These languages are based on a mathematical framework that combines synchrony (time advancing in lockstep with clocks) and deterministic concurrency. The paper explores the synchronous philosophy, the challenges of maintaining deterministic behavior when combining synchronous communication with deterministic concurrency, and the successful industrial applications of these languages. Section II discusses the successful use of these languages in industry and their commercialization. Section III describes new technologies for compiling these languages, which have proven more complex than initially anticipated. Section IV outlines major lessons learned over the past 12 years. Section V addresses future challenges, including the limitations of synchrony. Section VI concludes with a discussion of the future of synchronous languages. The paper focuses on embedded control systems, which are typically safety-critical, such as flight control systems in flight-by-wire avionics and antiskidding or anticollision equipment in automobiles. The synchronous approach is based on a common mathematical framework that supports synchrony and deterministic concurrency. This framework allows for the design of systems that are both mathematically sound and engineer-friendly. The paper discusses the fundamentals of synchrony, including the need for a solid mathematical foundation to reason formally about system behavior, which facilitates certification and improves implementation. It also explores the challenges of combining synchrony and concurrency while maintaining a simple mathematical model. The paper discusses the approaches taken by the synchronous languages to address these challenges, including microsteps, acyclic systems, unique fixpoints, and relations or constraints. The paper also discusses how the fundamentals of synchrony have been instantiated in the synchronous languages Lustre, Esterel, and Signal. It describes the features of each language, including their dataflow models, clock mechanisms, and activation conditions. The paper also discusses the variants and extensions of the synchronous language model, as well as the successful industrial applications of these languages in areas such as aerospace and automotive systems. The paper concludes with a discussion of the future of synchronous languages and their potential for further development and application.The paper discusses the evolution of synchronous languages over the past 12 years, highlighting their advancements, challenges, and successes. Synchronous languages, such as Esterel, Lustre, and Signal, have become a key technology for modeling, specifying, validating, and implementing real-time embedded systems. These languages are based on a mathematical framework that combines synchrony (time advancing in lockstep with clocks) and deterministic concurrency. The paper explores the synchronous philosophy, the challenges of maintaining deterministic behavior when combining synchronous communication with deterministic concurrency, and the successful industrial applications of these languages. Section II discusses the successful use of these languages in industry and their commercialization. Section III describes new technologies for compiling these languages, which have proven more complex than initially anticipated. Section IV outlines major lessons learned over the past 12 years. Section V addresses future challenges, including the limitations of synchrony. Section VI concludes with a discussion of the future of synchronous languages. The paper focuses on embedded control systems, which are typically safety-critical, such as flight control systems in flight-by-wire avionics and antiskidding or anticollision equipment in automobiles. The synchronous approach is based on a common mathematical framework that supports synchrony and deterministic concurrency. This framework allows for the design of systems that are both mathematically sound and engineer-friendly. The paper discusses the fundamentals of synchrony, including the need for a solid mathematical foundation to reason formally about system behavior, which facilitates certification and improves implementation. It also explores the challenges of combining synchrony and concurrency while maintaining a simple mathematical model. The paper discusses the approaches taken by the synchronous languages to address these challenges, including microsteps, acyclic systems, unique fixpoints, and relations or constraints. The paper also discusses how the fundamentals of synchrony have been instantiated in the synchronous languages Lustre, Esterel, and Signal. It describes the features of each language, including their dataflow models, clock mechanisms, and activation conditions. The paper also discusses the variants and extensions of the synchronous language model, as well as the successful industrial applications of these languages in areas such as aerospace and automotive systems. The paper concludes with a discussion of the future of synchronous languages and their potential for further development and application.