Bone marrow is a precursor for stem cells that have a capacity to produce all cell types: Blood cells like RBCs, WBCs and platelets start out from young (immature) cells called hematopoietic stem cells. Bone marrow in the post-natal has been seen as an organ composed of two main rooted systems that have in distinct lineage, the hematopoietic tissue proper and the associated supporting stroma. Evidence for this stem cell upstream of the diverse lineages and cell phenotypes and comprising the bone marrow stromal system has made marrow the only known organ in which two separate and distinct stem cells and dependent tissue systems not only coexist, but functionally cooperate (Bianco et al 2001).
The differentiation potential of marrow stromal cells into neural tissue or muscle grant it makes a membership in the diverse family of putative somatic stem cells. These cells exist in a number of post-natal tissues that have a capacity to differentiate into cell types phenotypically unrelated to the cells in their tissue of origin.