History of Insulin
The discovery and development of insulin as a medical treatment can be traced back to the 19th century.
Research into the development of insulin has driven scientists to take significant steps towards understanding human biology and a number of Nobel Prizes have been awarded for research into the hormone.
Discovery of endocrine role of the pancreas
1869: Paul Langerhans, a medical student in Berlin discovers a distinct collection of cells within the pancreas. These cells would later be called the Islets of Langerhans.
1889: Oscar Minkowski and Joseph von Mering remove the pancreas from a dog to study the effects on digestion. Sugar is found in the dogs urine after flies were noticed to be feeding off the urine.
1901: Eugene Opie discovers that the Islets of Langerhans produce insulin and that the destruction of these cells resulted in diabetes
Experimental usage of insulin
1916: Romanian Professor, Nicolae Paulescu, develops an extract of the pancreas and shows that it lowers blood sugar in diabetic dogs. World War I prevents the experiments from continuing and it is not until 1921 that Paulescu publishes evidence of the experiments. 
1921: In Toronto, Canada, Dr Frederick Banting and medical student Charles Best perform experiments on the pancreases of dogs. Professor John Maceod provided Banting and Best with a laboratory and dogs to carry out the experiments. The pancreas of a dog was removed, resulting in the dog displaying the signs of diabetes.
The pancreas was sliced and ground up into an injectable extract and injected a few times a day into the dog which helped the dog to regain health.
Given the early success, Macleod wanted to see more evidence that the procedure worked and provided pancreases from cows to make the extract which was named ‘insulin’.
Bertram Collip, a biochemist, joined the research team to provide help with purifying the insulin to be used for testing on humans. Banting and Best clearly had confidence in the insulin as they were the first humans to test the insulin by injecting themselves with it which caused them to experience weakness and dizziness, signs of hypoglycemia.
After the group had experimented enough to gain an understanding of the required doses and how best to treat hypoglycemia, their insulin was deemed ready to tried on patients.
First usage of insulin as a medical treatment
1922: The first patient, Leonard Thompson a 14 year old boy with type 1 diabetes is given the first medical administration of insulin. Previously patients with type 1 diabetes would be put onto starvation diets and would have only months to live. Leonard lived another 13 years before succumbing to pneumonia.
1922: As news of insulin’s success spread, Banting and Best begin receiving letters asking for help for others with type 1 diabetes. Banting and Best improve their techniques for the production of insulin and Eli Lilly becomes the first insulin manufacturer.
1923: Banting and Macleod are awarded the Nobel Prize in Physiology or Medicine. Banting and Macleod, however, felt Best and Collip were equally eligible and shared their prize money with the two colleagues. 
1936: Hans Christian Hagedorn discovers the action of insulin can be prolonged with the addition of protamine.
1950: NPH, an intermediate acting insulin, is marketed by Danish company Novo Nordisk.
Sequencing and synthesis of insulin
1955: Insulin is sequenced by Frederick Sanger, and is the first protein to be fully sequenced. In1958 Sanger receives the Nobel Prize in Chemistry for his research in this area.
1963: Insulin becomes the first human protein to be chemically synthesised.
1978: Insulin is then the first human protein to be manufactured through biotechnology, using bacteria to grow the insulin protein by a company called Genentech.
1982: Synthetic insulin is named ‘human insulin’ marking it as distinct from insulin derived from animals. Human insulin has the advantage of being less likely to allergic reactions than animal insulin. Humilin, manufactured by Eli Lilly, becomes widely available through the 1980s.
1996: Eli Lilly markets the analogue insulin lispro under the trade name Humalog. Analogue insulin is a genetically modified form of insulin whereby the amino acid sequence is altered to change how the insulin is absorbed, distributed, metabolised and excreted.