The cells are isolated from normal human adult tissues of the airways (nasal mucosa, trachea, bronchi, and distal respiratory tract), breast (mammary gland), kidney (whole kidney and renal cortex), and the placenta (amniotic membrane). Shortly after isolation, all AcceGen Biotech Human Epithelial Cells are cryopreserved at passage 2 (P2) . Each cryo vial contains more than 500,000 viable cells after thawing. Proliferating cell cultures are made from 500,000 cryopreserved cells that have been thawed and cultured for three days at AcceGen Biotech.