Historical description of first insulin trials just after its discovery. The review includes first initiatives of insulin treatment. The probability of other trials, not reported to the Insulin Committee of the University of Toronto and conducted in the years 1922 and 1923, is quite low. (1) Archival Collections, University of Toronto: Insulin Discovery and Early Developments of Insulin (University of Toronto Libraries digital special collection, with a particular section entitled "From a Patient's Point of View" containing letters, patient charts, newspaper clippings, and photographs). (2) Thomas Fisher Rare Book Library: Academy of Medicine Collection, F. G. Banting Papers, C. H. Best Papers, J. B.Collip Papers, W. R. Feasby Papers, E. Hugues Papers, J. J. R. Macleod Papers. (3) National Library of Medicine: PubMed search for the topic of history of insulin, History of Medicine-on syllabus archive. (4) Selected Journals for History of Medicine: Bulletin of the History of Medicine, Journal of the History of Medicine and Allied Sciences, Medical History. (5) Selected books: The Discovery of Insulin (M. Bliss); Diabetes, Its Medical and Cultural History (D. von Engelhardt); H. C. Hagedorn and Danish Insulin (T.Deckert), Continuing Quest (W. A. Tomkins). This historical review shows the quick progress from impure pancreatic extract to the selective isoelectric precipitation of the hormone, which made possible the introduction of insulin in the clinic. The coordination between the Departments of Physiology (Connaught Laboratories) and Medicine (Toronto General Hospital) was essential for the discovery and implementation of insulin therapy. The Insulin Committee was decisive for the negotiation with the pharmaceutical industry, the purification, grand-scale production, patents' achievement, and provision of licenses to expert clinicians and prestigious health centers. At the end of the year 1923, insulin treatment was already extended to Europe (mainly Scandinavia, Great Britain, and Spain). Insulin discovery and treatment changed the clinical spectrum of diabetes.