False-colour transmission electron micrograph (TEM) showing cells of an islet of Langerhans, the endocrine component of the human pancreas. At right in green, yellow & brown are insulin- secreting beta cells; in red at left are alpha cells, which secrete glucagon. The hormones insulin & glucagon are involved in carbohydrate metabolism. Insulin promotes the uptake of glucose by most cells, whilst (generally) glucagon counteracts the effects of insulin. A third group of delta cells (bottom, orange) secrete the digestive hormone somatostatin. Magnification: x6,000 at 6x7cm size, x2,700 at 35mm size.