Blood cells are made in the bone marrow. The bone marrow is the soft, spongy material in the center of the bones. It produces about 95% of the body's blood cells. Most of the adult body's bone marrow is in the pelvic bones, breast bone, and the bones of the spine.

Where does cell production occur?

Within the bone marrow, all blood cells originate from a single type of unspecialized cell called a stem cell. When a stem cell divides, it first becomes an immature red blood cell, white blood cell, or platelet-producing cell.

Which body part produces cells?

This is the cell's control center. Cells continually divide to make more cells for growth and repair in your body. The nucleus contains the information that allows cells to reproduce, or make more cells.