HaCaT cells. Immunofluorescence light micrograph of three HaCaT cells. Their nuclei, which contain the cells' genetic information in the form of deoxyribonucleic acid (DNA), are blue. HaCaT cells are human skin cells (keratinocytes) that have been transformed (mutated) to be immortal. They have unlimited growth potential, but unlike other immortal cell lines they are not tumourigenic (tumour forming). This means they grow in an orderly fashion and retain all the structural and functional features of human skin. HaCaT cells are grown in the laboratory, on dishes or mice, and are used in research, including wound healing research.