The pituitary gland is a small organ at the base of the brain that produces many important hormones and is a key part of the body's endocrine system. Disruptions in the pituitary have been associated with growth disorders, and vision problems including blindness.  Yoshiki Sasai, from the RIKEN Center for Developmental Biology (Japan), and colleagues designed a three-dimensional culture, on which researchers grew both pituitary gland and hypothalamus tissue, allowing the stem cells to self-assemble into a mouse pituitary gland. The team then tested the functionality of their synthesized organs by transplanting them into mice with pituitary deficits. The transplants were a success, restoring levels of glucocorticoid hormones in the blood and reversing behavioral symptoms, such as lethargy. Mice implanted with stem-cell constructs that hadn't been treated with the right signaling factors, and therefore weren't functional pituitary glands, did not improve.  The researchers plan next to attempt the experiment with human stem cells, and estimate it will take them another three years to synthesize human pituitary tissue. Perfecting the transplantation methods in animals will likely take another few years.