What landmark discovery regarding insulin was made in 1921?

In 1921, the landmark discovery regarding insulin was that it was identified as a treatment for diabetes. This was a significant breakthrough in medical science, as diabetes, particularly Type 1 diabetes, had previously been a life-threatening condition with no effective treatment available. With the discovery made by Frederick Banting and Charles Best, insulin was shown to effectively lower blood sugar levels and manage the symptoms of diabetes, dramatically improving the quality of life for those affected by the disease. This advancement not only provided a means of treatment but also changed the perception of diabetes from a fatal illness to a manageable chronic condition, paving the way for further research and developments in diabetic care.