Insulin's centenary: the birth of an idea.

At 2:00 h on Oct 31, 1920, Frederick G Banting, a surgeon practising in London, ON, Canada, conceived an idea to isolate the internal secretion of the pancreas. The following week, he met with noted scientist John J R Macleod in Toronto, ON, Canada, and they developed a research plan. By August, 1921, Banting and his student assistant Charles H Best had prepared an effective extract from a canine pancreas. In January, 1922, biochemist James B Collip isolated insulin that was sufficiently pure for human use. On Oct 25, 1923, Banting and Macleod received the Nobel Prize in Physiology or Medicine for the discovery of insulin. Here, we recount the most relevant events before and after the fateful early morning of Oct 31, 1920, which culminated in the discovery and clinical use of insulin.