On Friday 3 December Karolinska University Hospital and Karolinska Institutet jointly organized the Olof Norlander Memorial Day Symposium on Frontiers in Airway and Respiratory Physiology. Awardee of the Olof Norlander’s Honorary Lecture 2021 was Professor Mike Grocott, University of Southampton, UK. See his fantastic talk about the emergence and expansion of complex eukaryotic life on Earth and how we evolved to breathe oxygen: