Bone marrow is a soft, spongy tissue found inside certain bones, such as the femur and pelvis. It plays a crucial role in producing blood cells, including red blood cells, white blood cells, and platelets. These cells are essential for transporting oxygen, fighting infections, and aiding in blood clotting. There are two types of bone marrow: red marrow and yellow marrow. Red marrow is responsible for blood cell production, while yellow marrow mainly stores fat. As people age, some red marrow is gradually replaced by yellow marrow, but red marrow remains active in producing blood cells throughout life.