In the first step of the creative process, Karle and a team of experts scanned the bones of a female hand as the basis for a digital model. Then they gave the model pores and other microstructures that make it mimic bone. Karle 3-D-printed this scaffolding out of a biodegradable, nontoxic hydrogel. Finally, the team seeded the hydrogel with human stem cells and placed it in a bioreactor—a container to keep the project alive. Over the next two years, Karle wants the cells to grow over the frame and develop into bone.