Human cell lines are immortalized cells propagated in vitro from primary explants of human tissue or body fluid. The use of human cell cultures as a model for more complex biological systems is an integral part of molecular biology, and biomedical research. Cell culture studies provide greater understanding in the areas of developmental biology, protein and gene expression, as well as genetic evolution. You may establish your own human cell lines or choose to buy established cell cultures from commercial suppliers or non- profit cell banks. All human cell lines must be handled as potential biohazards unless characterized by testing to be free of bloodborn pathogens.