Blood cells begin in the bone marrow, the soft, spongy material in
the center of most large bones in the body. They begin as a hematopoietic
cell, more commonly known as a “stem cell,” and either mature in the marrow
or travel to other parts of the body where they mature into functioning blood
cells. The spleen, liver, and lymph nodes are also involved in the blood cell
production process, medically known as hematopoiesis.