RSC Publishing provides a compact overview of the application of bioprinting technologies: "In order to build an organ, you need four components: cells (the bio-ink), a biomaterial (the biopaper), a device to make three-dimensional structures (the bioprinter), and a method to aid tissue assembly and maturation (the bioreactor). In addition to this shopping list, you need the expertise to put the components together, and you need funding. Enter the hydrogel chemists, the cell and developmental biologists, the physicists, the computational modellers, and a company that builds rapid prototyping devices. ... in many ways, the biomaterial is the easy part. Shaping an artificial 'neo-organ', developing the printing tools and a computer model for layer-by-layer construction, and devising a strategy to mature the neo-organ before transplantation are among the main challenges." If you can build organs from a patient's cells - or even meaningful amounts of undamaged tissue for transplant - that will make an enormous difference to the future of health and longevity.