Sharpy-Shafer (1916) proposed that diabetes is due to failure of pancreas to secrete a chemical named insulin. Banting and Best (1921) first of all isolated insulin from dogs pancreas and used it for curing diabetes patients. Insulin is now obtained from pancreas of slaughtered pigs and cattle. This insulin slightly differs from mans insulin and effectively controls diabetes. By using genetic engineering or recombinant DNA technology, insulin producing genes from human beings have been transferred into E.coli bacteria, which produce insulin called humulin for clinical use. This type of synthetic insulin was produced by an American pharmaceutical firm Eli-Lily on July 5, 1983.