Red marrow is a type of bone marrow found in certain bones, such as the pelvis, sternum, and vertebrae. It is responsible for producing blood cells, including red blood cells, white blood cells, and platelets. This process is known as hematopoiesis, which is essential for maintaining a healthy circulatory and immune system. In adults, red marrow is primarily located in the flat bones, while in children, it is found in the long bones as well. As people age, some red marrow is replaced by yellow marrow, which is mainly composed of fat cells. However, red marrow remains crucial for blood cell production throughout life.