Coloured scanning electron micrograph (SEM) of a section through a parotid salivary gland, showing a number of serous secretory granules (small, spherical), within the serous glands. Serous glands contain serous acini, a grouping of serous cells that secrete a fluid (saliva) containing enzymes such as alpha amylase. The two parotid glands are the largest of the salivary glands. Magnification: x265 when printed 10 centimetres wide.