The authors highlight that the population of 65 years and more will duplicate on the planet to 2040. They assert that this change in the demographic structure will reshape the global economy, as well as the main places where people live and work. They also point to three key objectives in this book: 1. Generation of conclusive evidence showing the existence of residential segregation of the population in the Metropolitan Area of Mexico City (AMCM); 2. Identify and dimension the priority areas of attention within the AMCM (i.e. where are segregated older adults and how many they are), and 3. Compilation of best practices around the world in matter of the cities ability to older adults, what constitutes a set of social-political tools with a gerontological focus.