Salivary gland tissue. Coloured scanning electron micrograph (SEM) of a freeze-fractured sample of tissue from a salivary gland. A serous cell of the parotid salivary gland is the main structure seen here. Serous cells produce serous fluid, a common bodily fluid that is found in saliva. At centre right is the cell nucleus (red). Other cell organelles and structures visible are the Golgi apparatus (purple), the endoplasmic reticulum (green), cellular granules (yellow and light green) and mitochondria (blue). Magnification: x5300 when printed at 10 centimetres across.