The islets of Langerhans are the clusters of cells of the endocrine portion of pancreas. These contain 4 types of cells: (i) Alpha cells (32-38%) secreting glucagon (ii) Beta cells (60-70%), secreting insulin, (iii) Delta and F-cells (2-8%), secreting somatostatin. The three different type of cells are of different shape and size, present in different locations.