The New Scientist reports on an advance in dental regenerative medicine: "a Japanese team has successfully grown replacement teeth and implanted them into the mouths of adult mice, suggesting that a similar technique could replace missing teeth in humans. [The researchers] took single-tooth mesenchymal and epithelial cells - the two cell types that develop into a tooth - from mouse embryos. They stimulated these cells to multiply before injecting them into a drop of collagen gel. Within days, the cells formed tooth buds - the early stage of normal tooth formation. The team then transplanted these tooth buds into cavities left after they had extracted teeth from adult mice. There, they developed into teeth with a normal structure and composition. The engineered teeth also developed a healthy blood supply, and nerve connections. ... Since mesenchymal and epithelial cells have the potential to develop into other organs and hair follicles, Tsuji hopes his method could eventually be applied more widely." The past few years have seen rapid progress in the tissue engineering of replacement teeth; we should expect to see the same for other simple organs in the years ahead.