Bone marrow is a tissue that shows a strong blood supply. It accounts for just 5% of the human body mass. The functions it performs are invaluable to the human body. As scientific research and the observations of doctors show, only a small number of people know how to become an unpaid bone marrow donor. We also have no knowledge of what this tissue is and how important its function is. What do we need to know about bone marrow? How do you become an unpaid bone marrow donor?