Bones might seem rock-solid, but they're actually quite porous inside. Most of the large bones of your skeleton have a hollow core filled with soft bone marrow. Marrow's most essential elements are blood stem cells and for patients with advanced blood cancers like leukemia and lymphoma, the best chance for a cure is often a bone marrow transplant. How does this procedure work? Melody Smith explains. [Directed by Artrake Studio, narrated by Bethany Cutmore-Scott, music by Harlan Hodges / WORKPLAYWORK].