Breast tissue. Light micrograph of a section through tissue from a mammary gland, or breast. One of the breast lobules is seen here, composed of numerous alveolar ducts (purple). During pregnancy the epithelial cells of these ducts proliferate in preparation for milk secretion after birth. Within the lobule the ducts are separated by loose, highly vascular connective tissue (blue). The connective tissue that lies between the lobules in a breast is denser and more fibrous (for example, centre left). Trichrome blue stain. Magnification unknown.