Blood cell formation, also known as hematopoiesis, occurs primarily in the bone marrow, where stem cells differentiate into various types of blood cells. These stem cells can develop into red blood cells, white blood cells, and platelets, each serving essential functions in the body. Red blood cells transport oxygen, white blood cells are crucial for the immune response, and platelets play a key role in blood clotting. The process of blood cell formation begins with multipotent hematopoietic stem cells, which undergo a series of stages to become mature blood cells. Growth factors and cytokines regulate this process, ensuring the body produces the right amount of each cell type to maintain overall health and respond to physiological needs.