Megacities are gaining importance as hubs of globalisation processes in a world increasingly dominated by cities. A deeper understanding of the multiple causes and drivers of their development is needed in order to shape the global urban transformation towards sustainability. The interdisciplinary research programme "Megacities - Megachallenge: Informal Dynamics of Global Change" aimed at understanding the connections between informal mega-urban processes and global change by investigating the situation in the two mega-urban areas of the Pearl River Delta/China and Dhaka/Bangladesh. The research focused on processes and interactions in four fields with high development dynamics and social relevance: new forms of governance and self-organisation, differentiation of urban economies, dynamics of matter and resource flows, and informal settlement development.