High magnification light micrograph of a human pancreas showing the boundary between an islet of Langerhans (lighter coloured, left) and the exocrine serous acini (darker coloured, right). Unlike exocrine cells, which form rounded units (acini) with abundant serous grains in the center, the endocrine cells of the islet have a pale cytoplasm and are organized in cords. Among the cords there are connective septa where the capillaries are located.