Recent research highlights key challenges and opportunities in citizen and community science for biodiversity research. The "science of citizen science" requires further exploration of core research questions, methodologies, and supporting technologies. Citizen science data are increasingly important for scientific studies, particularly in biodiversity and pollution research and for monitoring Sustainable Development Goals. However, improvements in data stewardship practices are needed to maximise the benefits for science and society. Frontiers for future research include sampling underrepresented taxa and regions, estimating species abundance from presence data, and understanding ecological and species interactions. Outstanding challenges involve observer behaviour, non-structured but opportunistic sampling, statistical models, and communication with the local and underrepresented communities –with potential solutions including collecting additional metadata, combining datasets, refining analytical methods, and reevaluating research goals. The session welcomes anyone involved in connecting citizen or community science with biodiversity research, at any scale—from community-driven local projects to large crowd-sourced data initiatives. We aim to highlight the scope, challenges, and potentials of citizen science contributions to biodiversity research, conservation efforts, and how these incorporate and benefit the communities directly involved.