Light micrograph of lactating human mammary gland. Visible is a field of alveoli, which are produced from terminal tubules of the pre-lactation mammary gland. Each appears as a layer of epithelial cells with purple nuclei enclosing a central space. Many of these spaces contain pink masses of secreted material, comprising droplets of fat and cytoplasmic debris - a few nuclei can be seen (purple dots). At the base of the picture, in pink, is the connective tissue which comprises the stroma of the gland and contains the lactiferous ducts (not shown here). Magnification x50 at 35mm size.