This chapter reports on a study of communication related to the emerging scientific practice of citizen science, a practice with multiple definitions, but which, in simplest terms, denotes "participation by the public in a scientific project". It argues that, while roughly distinguishable as communication between expert scientists and communication about science with non-experts, the two are more interrelated than commonly understood and that this interrelationship is a force for mutual change and influence. Taking a case study, this chapter draws on author's ethnographic work with the Heartbeats Project, a citizen science project run by a biology lab actively engaged in innovating with scientific communication and embracing the blurred boundaries between expert and non-expert that citizen science encourages. The Heartbeats Project underscores how citizen science also contributes to the forces for change in scientific genres and genre networks. The Heartbeats Project case presents several findings relevant for those engaged in or teaching scientific communication in a shifting rhetorical landscape of science.