Children and young people, throughout the world, are experiencing a time of immense and rapid change - environmental, social, political, economic, and cultural. This chapter introduces readers to a volume entitled Geographies of Global Issues: Change and Threat, which is part of the Geographies of Children and Young People series. It provides an overview of the chapters contained in that volume and outlines four key themes that run across those chapters. First, children's geographies are also - fundamentally - about adults. It does not make sense to do children's geographies, without taking the perspectives of adult decision-makers into account. Second, children and young people are agents of change - but their lives are also powerfully influenced by broader structures and processes over which they have little say. Children's geographers need to balance their attentiveness to the microscale of children's everyday lives, with a careful and sustained focus on the bigger picture. Third, change is not just an external force that impacts on children and young people's lives. Children and young people contribute to diverse global, regional, and local changes and threats. It is important to bear in mind that their contributions to change are not always benign or beneficial. Fourth, while change can threaten or undermine children and young people's wellbeing, it can also engender opportunities. Children's geographers have an important role to play in scratching beneath the surface, to uncover sources of possibility and optimism amidst upheaval.