In medi­ci­ne, trans­fer­ring human mate­ri­al from one indi­vi­du­al to ano­t­her is cal­led trans­plan­ta­ti­on. Des­pi­te the equi­va­lence of the term “trans­plan­ta­ti­on” and the com­ple­xi­ty of the under­ly­ing legal regu­la­ti­ons, a firm dis­tinc­tion must be made bet­ween the trans­plan­ta­ti­on of stem cells and that of other organs and tis­su­es or other body parts. Stem cells are a rege­ne­ra­ti­ve tis­sue in the body which are taken from a spe­ci­fi­cal­ly selec­ted donor – usual­ly an adult. As a com­ple­te immu­ne sys­tem is trans­plan­ted rather than nor­mal body cells only, the requi­re­ments for an HLA match are much hig­her and the medi­cal con­di­ti­ons far more com­plex (allo­gen­eic trans­plan­ta­ti­on, auto­lo­gous transplantation).