A bone marrow transplant is a medical procedure that replaces damaged or diseased bone marrow with healthy bone marrow. Bone marrow is the soft tissue inside bones that produces blood cells. This treatment is often used for patients with conditions like leukemia or lymphoma, where the bone marrow is not functioning properly. During the transplant, doctors collect healthy stem cells from a donor's bone marrow or blood. These stem cells are then infused into the patient’s bloodstream, where they travel to the bone marrow and start producing new blood cells. This process can help restore the body’s ability to fight infections and produce healthy blood.