Pituitary gland. Coloured transmission electron micrograph (TEM) of cells in the anterior pituitary gland, a hormone-secreting gland at the base of the brain. The cells' nuclei, which contain their genetic information, are dark green. The cell at centre is a somatotroph cell, a secretory cell that has granules (purple) containing hormones to be secreted in its cytoplasm (olive green). Somatotrophs secrete human growth hormone, which promotes growth and controls numerous metabolic processes.