Book excerpt: The first “urban century” in history has arrived: a majority of the world’s population now resides in cities and their surrounding suburbs. Urban expansion marches on, and the planning and design of future cities requires attention to such diverse issues as human migration, public health, economic restructuring, water supply, climate and sea-level change, and much more. This important book draws on two decades of pioneering social and ecological studies in Baltimore to propose a new way to think about cities and their social, political, and ecological complexity that will apply in many different parts of the world. Readers will gain fresh perspectives on how to study, build, and manage cities in innovative and sustainable ways.