From ScienceDaily: "This is the first successful artificial bone marrow. It has two of the essential functions of bone marrow. It can replicate blood stem cells and produce B cells. The latter are the key immune cells producing antibodies that are important to fighting many diseases ... Bone marrow is a complicated organ to replicate ... Vital to the success of this new development is the three-dimensional scaffold on which the artificial marrow grows. This lattice had to have a high number of precisely-sized pores to stimulate cellular interaction. The scaffolds are made out of a transparent polymer that nutrients can easily pass through. To create the scaffolds, scientists molded the polymer with tiny spheres ordered like billiard balls. Then, they dissolved the spheres to leave the perfect geometry of pores in the scaffold. The scaffolds were then seeded with bone marrow stromal cells and osteoblasts, another type of bone marrow cell."