Light micrograph of normal female breast (mammary gland) tissue from a non-pregnant woman, showing aggregations of glandular lobules (more apparent at lower right of image). Lobules are the milk- secreting areas of the breast, each consisting of an aggregate of branching ducts, called alveolar ducts, which end as blind- ended ductules (seen here). Alveolar cells (small dark dots are cell nuclei) in the walls of the ducts are responsible for synthesis of milk. The alveolar duct epithelium proliferates during pregnancy under hormonal control (prolactin is a key hormone) in preparation for full-scale milk production after childbirth. Mag: X 100 at 6x7cm, X42 at 35mm size.