The 'islets of Langerhans' are found in
Pancreas
The islets of Langerhans were first found by a German medical student Paul Langerhans.
There are three kinds of islets of Langerhans found in the pancreas - α-cells, β-cells and δ-cells.
α-cells secrete glucagon, β-cells secrete insulin and δ-cells secrete somatostatin.