Certain cells in the body that can grow into other kinds of cells. There are two kinds of stem cells - embryonic stem cells and non-embryonic (adult) stem cells. BoneMarrowTest.com does not deal in any way with embryonic stem cells taken from the unborn. Our focus is on testing adult stem cell donors for patients suffering from leukemia and other diseases whose lives can be saved via adult stem cell donation. Adult stem cells include bone marrow stem cells, umbilical cord blood stem cells, and peripheral blood stem cells (PBSC).