Stem cells used in therapy include mainly hematopoietic stem cells (HSC) to treat aplasias, leukemias and hematological genetic diseases, and mesenchymal stem cells (MSC) produced in small quantities by the bone marrow, but also other tissues, to treat cardiac and cutaneous diseases thanks to their secretory properties of growth factors. A major step was taken with the use of embryonic (ESC) or induced pluripotent stem cells (iPS). The former are used, after isolation and differentiation, either in rare therapeutic purposes or for the in vitro screening of drugs. iPS are produced from adult cells after reprogramming and differentiation and utilized for the treatment of various diseases in autologous or allogeneic form, the second condition allowing only mass production. New lines of research are now in progress including the creation of organoids that are templates of many organs of the body and allow the process of cell organization and its perturbations to be analyzed. Creation of post-meiosis gametes (23 chromosomes) from iPS or ESC is intended to treat serious genetic diseases. Creation of human chimera by interspecies blastocyst complementation has also been studied in view of organ transplantation. It is only allowed for the implantation of human cells in animal blastocysts and prohibited for the reverse. Implantation in uterus of the modified embryos is prohibited by the French law.