This document discusses citizen science, which involves members of the public engaging in authentic scientific research such as asking questions, collecting data, and interpreting results. It describes different levels of participation from contributory to collaborative to co-created and discusses how projects can be designed to maximize participation and outcomes for science, social systems, and individuals. The key aspects that determine participation include the degree, quality, numbers reached, depth of engagement, and timing. The document argues that with the right design, citizen science projects offer vast possibilities for public participation in scientific work.