The discovery of insulin in 1921 is undoubtedly one of the most significant medical discoveries of the 20th century. Frederick Banting is considered as the main discoverer since he was the one who had the idea of tying a ligature round the pancreatic canals in order to provoke diabetes. when he was still a young surgeon in London, ontario (Canada), he met JJR Macleod of the University of Toronto and suggested experimenting with this procedure in dogs. Not entirely convinced, professor Macleod provided him with the necessary research laboratory and offered the services of a young science student, Charles Best. They started their experiments during the summer of 1921. The dogs indeed developed diabetes. The pair then tested various pancreas extracts in order to – or so they hoped – cure the diabetes. After numerous trials, they managed to stabilize the glycaemia of one of their guinea pigs. Marc Aras takes up the story of a truly great Canadian achievement.