Citizen science—research involving nonprofessionals in the research process—has attracted both strong enthusiasts and detractors. Many environmental professionals, activists, and scholars consider citizen science part of their toolkit for addressing environmental challenges. Critics, however, contend that it represents a corporate takeover of scientific priorities. In this timely book, two sociologists move beyond this binary debate by analyzing the tensions and dilemmas that citizen science projects commonly face. Key lessons are drawn from case studies where citizen scientists have investigated the impact of shale oil and gas, nuclear power, and genetically engineered crops. These studies show that diverse citizen science projects face shared dilemmas relating to austerity pressures, presumed boundaries between science and activism, and difficulties moving between scales of environmental problems. By unpacking the politics of citizen science, this book aims to help people negotiate a complex political landscape and choose paths moving toward social change and environmental sustainability.