[Human embryonic stem cells: practical problems and scientific potentialities].

Human embryonic stem cells (hESCs) are derived from pre-implantation embryos given to research with the informed consent of the parents. These cells cannot give rise to a human being: they are not totipotent. They have an unlimited self-renewal capacity and they can generate the three embryonic germ layers, their respective derivatives and the extra-embryonic tissues: they are pluripotent. These cells represent an outstanding material for understanding functional genomics of not yet characterized human genes. They will be an important tool for pharmaceutical and clinical research.