Breast tissue. Light micrograph of a section through healthy breast (mammary gland) tissue from a woman who is not pregnant. The glandular tissue, which will become capable of producing milk during pregnancy, is arranged in a lobule (purple). Adipose (fatty) tissue (white circles) and fibrous connective tissue (blue) separate lobules. The lobules are arranged to form 15 to 20 lobes, which drain via the milk-bearing lactiferous ducts to separate openings at the surface of the nipple.