The International Institute for Applied Systems Analysis (IIASA), in collaboration with its Japan National Member Organization (NMO), supported by Ministry of the Environment Japan (MOEJ) has initiated a joint research endeavor centered on Cities Transformation. The primary aim of this collaborative effort's inaugural phase is the compilation of a fast-track comprehensive report. This report aims to consolidate the current understanding of urban transformations, identifying critical knowledge gaps therein. It serves to support the scientific community, city stakeholders, and policy-makers in discerning areas warranting greater attention and, crucially, further investigation and study. Particularly, it provides updates on the IPCC 7th Assessment Cycle, with a specific focus on its Special Report on Climate Change and Cities. Commencing with an overview of global urbanization trends, the report delves into the status of informal urban settlement development (Section 2). Subsequently, it comprehensively discusses the physical aspects of climate change, including impacts, vulnerability, adaptation, and mitigation, with a spotlight on air pollution and waste challenges (Section 3). Section 4 shifts focus to systems transformation, examining sectors and cross-cutting perspectives through various case studies. Following this, Section 5 investigates the enabling conditions for city transformations, emphasizing the roles of governance, behavioral and lifestyle changes, innovation and technology, and finance. Expanding further, Section 6 assesses the synergies and trade-offs of mitigation and adaptation strategies, with a particular lens on Sustainable Development Goals (SDGs), health, and well-being. The report concludes by recognizing significant knowledge gaps highlighted through expert insights. We had the privilege of interviewing several experts in the field, including Xuemei Bai, Shobhakar Dhakal, Arnulf Grubler, and Ayyoob Sharifi. We extend our sincere appreciation to them for their valuable contribution. The resulting report will be launched during an international expert workshop and symposium to disseminate the project's findings to the broader public. The event is scheduled for February 27th to 28th, 2024, in Tokyo-Japan.