Blood cells are produced in the bone marrow of the body more specifically they become blood cells from first being stem cells which then divide until they reach a mature red blood cell stage. ( or other types of cells, stem cells are like the blank template for either red blood cells, white blood cells, or platelettes.)
Red blood cells, most white blood cells, and platelets are produced in the bone marrow, the soft fatty tissue inside bone cavities. Two types of white blood cells, T and B cells (lymphocytes), are also produced in the lymph nodes and spleen, and T cells are produced and mature in the thymus gland.
