Citizen science is a rapidly growing field with expanding legitimacy. Often seen as a cluster of activities under a larger umbrella of concepts, including ‘open science’ and ‘open innovation’, citizen science expands public participation in science and supports alternative models of knowledge production. This includes strengthening scientific research by engaging with a variety of topics and information sources, and fostering cross- or trans-disciplinary knowledge production. Citizen science can expand stakeholder participation and introduce new perspectives and informa-tion as well as new partnerships. Many projects are opening up cutting-edge areas of science, such as gene editing and synthetic biology, to new audiences, enabling a wider discussion about their societal implications. In these ways, citizen science projects are often initiated to address an immediate problem or research question, while also building capacity for communities to participate in science and shape policy decision-making and implementation in the longer term.