The winner of the 2021 Outstanding Paper Award in memory of Hans Jørgen G Gundersen is Nick Yao Larsen, the first author of the paper Larsen et al. (2021): Cellular 3D-reconstruction and analysis in the human cerebral cortex using automatic serial sections (Communications Biology 4, 1-15). This is the first instance of the annual award, intended to recognize best papers containing original work in the field of stereology, which are judged on scientific merit, technical and general quality, expected impact, originality, and relevance to stereology.