Light micrograph of normal female breast (mammary gland) tissue from a non-pregnant woman, showing aggregations of glandular lobules. The lobules are the milk-secreting areas of the breast, each consists of an aggregate of branching ducts, called alveolar ducts, which end as blind-ended ductules. Compound alveolar cells (visible here as the central vertical band of lobular tissue) 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. Magnification: x200 at 35mm size.