59 The Promise of Tissue Engineering“Bioartificial” pancreases, livers and kidneys. Freshly grown skin that can be bought by the yard. Honeycombs of collagen for breast reconstruction after mastectomy. Plastic-coated pellets of cells implanted in the spine to treat chronic pain. No, this isn’t science fiction: it’s tissue engineering, and as these pioneers in the field explain, it’s already changing people’s lives.Growing New Organs 60David J. Mooney and Antonios G. MikosResearchers have taken the first steps toward growing “neo-organs”—living, artificial human parts.Embryonic Stem Cells for Medicine 68Roger A. Pedersen These remarkable human cells, only recently isolated, could help repair damaged tissues.Encapsulated Cells as Therapy 76Michael J. Lysaght and Patrick Aebischer Many illnesses could be treated with cells packaged inside protective membranes.Skin: 83The First Tissue-Engineered Products Nancy Parenteau and Gail Naughton describe the manufacturers’technical and regulatory struggles.Tissue Engineering: 86The Challenges Ahead Robert S. Langer and Joseph P. Vacanti Ten obstacles to building organs from isolated cells.90 Is Space Finite?Jean-Pierre Luminet, Glenn D. Starkman and Jeffrey R. Weeks The universe may look infinitelylarge, but that could be an illusion. If space folds back on itself like the braids of a pretzel, it might be boundless, and light could spool around the cosmos endlessly. Astronomers are looking for patterns in the star field that could signal a finite volume for space.98 Alan Turing’s Forgotten Ideas in Computer ScienceB. Jack Copeland and Diane ProudfootNeural networks and hypercomputation are hot ideas for transcending the limits of traditional algorithmic computing. What few realize, however, is that both concepts were anticipated in detail decades ago by Alan Turing, the British genius better remembered for laying the groundwork for artificial intelligence.