This chapter lays out some of the general principles by which contemporary urbanisation and metropolitan areas can be approached by providing a brief literature review and an account of the scientific debate on urban studies to conceptualise and explain urban and metropolitan patterns and their development. The notion of the urban land nexus is presented as a useful analytical tool that incorporates the specificities of local history, land use, territory and politics in the study of urbanisation and urban development in diverse countries. Together with an overview of the historical drivers and waves of urbanisation, the chapter delivers a detailed account of recent international trends in urbanisation. Reports and up-to-date data from the World Bank and the United Nations reveal how international urban patterns vary significantly depending not only on location, but also on income levels and historic trajectories. Over time the urban population has largely been absorbed into megacities and cities with a population of 1 to 5 million. Remarkably, a quarter of the world’s population lives in supersized metropolitan areas that cut across jurisdictional boundaries.