" For about 60 years type 1 diabetics were treated with insulin extracted from the pancreas of pigs. This wasn’t ideal as the insulin was a relatively minor component of all the proteins in the pig pancreas and required a lot of expensive purification to produce a relatively small amount of the drug. The pig insulin wasn’t quite identical to the normal human version and it wasn’t suitable for some patients. It was also very difficult to ramp up supply quickly when demand increased. In the 1980s, the drug firm Eli Lilly produced and sold human insulin that had been created in genetically modified bacteria. Now, virtually all insulin is made in bacteria or yeast. "

― Nessa Carey , Hacking the Code of Life: How gene editing will rewrite our futures