The history of suburbs has received so much scholarly attention in recent decades that it is time to take stock of what has been established, in order to discern aspects of suburbs that are still unknown. To date, the main lines of inquiry have been dedicated to the origins, growth, diverse typologies, culture and politics of suburbs, as well as to newer topics such as the gendered nature of suburban space. The vast majority of these studies have been about particular times and places. The authors propose a new perspective on the study of suburbs, one which will begin to investigate the transformations of suburbs after they have been established. Taking the entire era from the mid-nineteenth century through to the late twentieth century as a whole, it is argued that suburbs should be subjected to a longitudinal analysis, examining their development in the context of metropolises that usually enveloped them within a generation or two of their founding. It is proposed that investigation of these ‘transitions’ should be undertaken in parallel with the changes that occur in the life-cycles of their residents. It is suggested that an exploration of the interaction of these factors will open a broad new research agenda for suburban history as a subfield of urban history.