Allotransplants (allo- from the Greek meaning "other") is the transplantation of cells, tissues, or organs, to a recipient from a genetically non-identical donor of the same species. The transplant is called an allograft, allogeneic transplant, or homograft. Most human tissue and organ transplants are allografts. A xenograft is a graft from a different species, such as when animal tissue is grafted into human tissue, or when human cancer cells are implanted in mice for experimental tumor studies. Allografts can be referred to as "homostatic" if they are biologically inert when transplanted, such as bone and cartilage.