The mammary gland consists of pseudostratified epithelia, with myoepithelila cells resting upon a basement membrane and apical glandular epithelial cells facing the lumen of the ducts and alveoli. Mammary epithelial cells undergo changes in growth, invasion, and differentiation throughout much of adulthood, and most strikingly during pregnancy, lactation, and involution. They proliferate and invade the surrounding extracellular matrix during the fetal and postnatal development of the gland, and then more vigorously at puberty as the branches of the mammary epithelial tree are formed.HMEpiC from AcceGen Research Laboratories are isolated from normal human breast tissue. HMEpiC are cryopreserved at passage one culture and delivered frozen. Each vial contains >5×10^5 cells in 1 ml volume. HMEpiC are characterized by immunofluorescent method with cytokeratine antibodies. HMEpiC are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HMEpiC are guaranteed to further expand for 15 population doublings in the conditions provided by AcceGen Research Laboratories