Abstract: With the growing social divide between formal and informal settlements, cities become dysfunctional. To deal with these challenges, cities have utilized conventional planning methods, social housing, and “Site and Services programs”. Due to the nature and magnitude of the informal urbanization process, however, they have had only limited success. This article provides an overview of my book, Planning and Design for Future Informal Settlements: Shaping the Self-Constructed City. This work sheds light on how to guide the sustainable growth of the predominantly informal city by providing criteria, clues for spatial organization, and performative mechanisms. Drawing from years of experience and research, it introduces the notion of Informal Armatures (IA) as a design and managerial approach to informal urbanization. Beginning from early stages of occupation, the approach also allows for agile transformations as the settlements evolve to become part of much larger urban systems. The IA approach derives from previous studies and projects, considering their planning and design principles and practical results. While analyzing emblematic Latin American examples, IA illustrates challenges common to the informal city globally. These challenges include: 1) the inadequacy of the sites where informal growth tends to occur, 2) deficient mobility and accessibility, 3) the difficulty of securing public or communal land required to provide services, jobs, amenities, and public spaces, 4) unbalanced urban systems, making informal areas highly dependent of the formal city. IA also deals with environmental strains, important issues in contemporary urbanism. It additionally highlights the need for innovative forms of public/communal and private cooperation to orient the urbanization process, as well as means to foster a culture of inclusion and peace. IA is a call for urgent action. Providing that there is political will, transparency, and technical skills to accompany the process of informal urbanization, IA offers simple, straight forward solutions to the challenges of informal settlements.