Things are getting smaller all the time; not just micro-small (a millionth) but nano-small, the prefix meaning a billionth. Given that the foreword is by artificial-intelligence authority Marvin Minsky, you might presume that ""things"" are computers and that getting smaller is ever more beautiful. And you would be right. Moreover, Minsky's bullish point of view is more than matched by Drexler, a research affiliate in the Space Lab at MIT. Essentially, Drexler builds a future whose foundations rest on the latest in biotechnology and computers. Molecular biologists have been able to use bacteria to manufacture molecules to order. Drexler envisions man-made assemblers of nano dimensions that could be programmed to stack atoms according to plan. In turn, assemblers could make replicators that would be analogous to DNA and RNA, the molecules that enable cells to divide or to make many copies of useful molecules like enzymes. Once the machines--the engines of creation--are small enough, there's no end to their utility in traveling through capillaries and invading cells (as viruses do) to repair defects or delay the aging process. Nanotechnology would also be applied in industry to build everything from self-repairing rocket engines to comfortable second-skin space suits. Yes, space is clearly important if people live longer and resources are limited. So light-sails and space colonies are also in the picture. Sci fi? Cockeyed optimism? A lot, yes, along with some blurry thoughts and misquotes. But Drexler is smart enough to address critics, pointing to how wrong history's naysayers have been, and looking on the dark side as well: evils of nanotechnology; totalitarian use of nanomachines. He posits the need for built-in safeguards lest the technology take over. Even with these strategies, many critics will raise questions about the targeting and control of nanodevices. Others will claim the whole business is preposterous. No doubt some of it is, but some of it may not be. Of interest to those who like to keep abreast of current computer controversies.