HeLa cells, multiphoton fluorescence micrograph (MFM). The cell nuclei, which contain the cells' genetic information, are blue. Golgi bodies, which modify and package proteins, are orange. Microtubules, protein filaments that make up part of the cytoskeleton, are green. The cytoskeleton maintains the cells' shape, allows some cellular mobility and is involved in intracellular transport. HeLa cells are a continuously cultured cell line of human cancer cells. They are immortal and so thrive in the laboratory. HeLa cells are widely used in biological and medical research.