A start-up called Organovo uses a 3D printer to build a variety of human tissue types, from cardiac muscle to blood vessels. The company hopes to eventually print entire organs for transplant from feedstock of a patient's own cells, thereby reducing the likelihood of rejection. But in the meantime, the 3D printed tissue could be used for drug testing. From Technology Review (photo Frank Rogozienski/Wonderful Machine):

Because Organovo's product is so similar to human tissue, it could help researchers identify drugs that will fail long before they reach clinical trials, potentially saving drug companies billions of dollars…<

Unlike some experimental approaches that have used ink-jet printers to deposit cells, Organovo's technology enables cells to interact with each other much the way they do in the body. They are packed tightly together and incubated, prompting them to adhere to each other and trade chemical signals.