The Fourth Plenary Session of the 20th Central Committee of the Communist Party of China emphasized the need to "accelerate the comprehensive green transformation of economic and social development to build a Beautiful China" and called for "firmly establishing and practicing the concept that lucid waters and lush mountains are invaluable assets, using the goals of carbon peak and carbon neutrality as a driving force, and synergistically promoting pollution reduction, carbon reduction, green expansion, and economic growth." As a vital component of the national strategic scientific and technological strength, the Institute of Urban Environment, Chinese Academy of Sciences (hereinafter referred to as IUE, CAS) deeply feels the immense responsibility and the great honor of its mission. We profoundly understand that we must closely integrate the study and implementation of the guiding principles of the Fourth Plenary Session of the 20th CPC Central Committee with the core task of the Chinese Academy of Sciences to "secure a strategic vantage point in science and technology," and deeply integrate it with the major research tasks and long-term development layout undertaken by IUE. Only by doing so can we live up to the expectations of our times and fulfill our mission.

Currently, China's urban development is at a critical juncture of transitioning from extensive expansion to intensive improvement. Traditional environmental governance models are facing diminishing marginal returns and struggle to support the realization of the goals for carbon peak and carbon neutrality. The call from the Fourth Plenary Session of the 20th CPC Central Committee to "synergistically promote pollution reduction, carbon reduction, green expansion, and economic growth" urgently requires systematic solutions provided by scientific and technological innovation. To this end, IUE is striving to accurately position itself and seek breakthroughs in serving the broader national agenda of green transformation. We have refined and proposed the strategic scientific vantage point of **"Self-Cleansing Cities."** By employing means such as multi-media collaborative governance and the combination of natural remediation with artificially enhanced self-cleansing, we aim to systematically improve the urban environment's self-cleansing capacity, thereby providing a new paradigm for the construction of green, low-carbon, and beautiful cities.

To achieve this goal, IUE has vigorously promoted the reform of its research organization model. Addressing issues such as the relatively small scale of previous research groups and the fragmentation of research directions, IUE broke down the barriers between these groups. It established five interconnected research centers and reorganized the original research groups into 15 innovation teams. Throughout this reform, we have adhered to the principle of combining top-level design with grassroots innovation, encouraging researchers to actively seek collaboration and contribute ideas. This has facilitated a transition from "physical merger" to "chemical integration," forming the "large-group" combat capability required to tackle key and core problems. By optimizing the innovation system, IUE has effectively enhanced the efficiency of research resource allocation and promoted the smooth connection of the innovation chain, providing a solid organizational foundation for producing major scientific achievements.

Currently, IUE is undertaking the National Science and Technology Major Project titled "Research, Development, and Demonstration of Metabolic Processes and Self-Cleansing Technologies for Typical City Organisms in the Beijing-Tianjin-Hebei Region." This project directly confronts the contradictions between resources and the environment in the region and strives to break through the dilemmas of traditional governance models. Closely adhering to the requirements of the Fourth Plenary Session of the 20th CPC Central Committee to "synergistically promote pollution reduction, carbon reduction, green expansion, and economic growth," the project aims to build a self-cleansing urban system, focusing on breakthroughs in three major technology systems: first, urban metabolism modeling and pollution source tracing technologies, which construct high-resolution spatiotemporal maps to accurately identify key junctures for pollution control; second, multi-media collaborative governance technologies, developing materials and equipment for artificially enhanced self-cleansing of atmospheric pollutants; and third, advanced urban water body purification technologies, creating ecologically enhanced integrated solutions. These technologies strongly support the transformation from end-of-pipe treatment to whole-process regulation. Through multi-scenario demonstration applications, the project establishes an environment-health-economy multi-dimensional assessment system and forms synergistic plans for emission reduction and capacity expansion, providing replicable technological pathways and engineering demonstrations for regional green transformation, directly serving the construction of a Beautiful China and the implementation of the "dual carbon" strategy.

Looking towards the 15th Five-Year Plan period, IUE will be guided by the principles of the Fourth Plenary Session of the 20th CPC Central Committee, thoroughly implement the decisions and deployments of the CAS Party Leadership Group, and systematically plan for future development, with the core goal of securing the strategic vantage point of "Self-Cleansing Cities." First, regarding the scientific and technological layout, we will focus on the theoretical system and technical methods for "Self-Cleansing Cities," establishing "Urban Metabolism and Health" and "Key Technologies for Urban Self-Cleansing" as two main research directions, and deploying "Multi-dimensional Intelligent Perception of the Urban Environment" and "Coordinated Control of Multi-media Pollution" as two frontier research directions, striving to produce a batch of major original achievements. Second, in terms of institutional mechanisms, we will deepen the reform of the research organization model, improve the science and technology evaluation and incentive mechanisms based on major national needs, strengthen "large-group" collaborative innovation, and enhance the overall effectiveness of the innovation system. Third, concerning the talent team, we will implement more open and effective talent policies, vigorously attract and cultivate strategic scientists and leading talents, and build high-level innovation teams. Fourth, regarding platform construction, we will accelerate the construction of research platforms such as the Urban Environment Big Data and Intelligent Decision-Making Platform and field observation and research stations, consolidate the foundational capabilities for scientific and technological innovation, and provide a solid guarantee for supporting the construction of a Beautiful China.

Through studying and implementing the guiding principles of the Fourth Plenary Session of the 20th CPC Central Committee, IUE has gained clearer direction, stronger confidence, and greater motivation. IUE will always bear in mind that, as the "national team" and "national citizen," we must concern ourselves with "national affairs" and shoulder "national responsibilities." Through concrete actions to secure the strategic vantage point of "Self-Cleansing Cities," we will bravely explore, pioneer, and innovate, striving to make new and greater contributions to accelerating the building of a leading nation in science and technology, realizing the Chinese Dream of the great rejuvenation of the Chinese nation, and constructing a Beautiful China where humanity and nature coexist in harmony.