Blood formation, also known as hematopoiesis, is the process by which the body produces blood cells. This occurs primarily in the bone marrow, where stem cells differentiate into various types of blood cells, including red blood cells, white blood cells, and platelets. Each type of cell has a specific function, such as transporting oxygen, fighting infections, or aiding in blood clotting. The process of blood formation is regulated by various growth factors and hormones, which ensure that the body maintains a balanced supply of blood cells. For example, the hormone erythropoietin stimulates the production of red blood cells in response to low oxygen levels. This complex system allows the body to adapt to changing needs and maintain overall health.