Brains, brains, brains. I discussed the shrinking point with my biology-teacher, and he came up with the following points: You can do it in two ways, you can mess with the genetics, or you could try it on a chemical base, and completley build the human from molecule to molecule..... The first way will probably give you a human from about the known dwarf size. The second way can be much smaller: The proportions must stay the same, so the ratio os differnt parts of the body will dictate the smallest possible size. BUT, there is one main problem, the complicated structure of the body will remain, and so the brains must have a minimum size (you could argue for a dumb creature, only able to move, but than it wouldn't be a human anymore). This brain size will be the problem. Cause when we make really small people with big heads to keep the brains in, it wouldn't be a human either, more a new life-form. Conclusion: we can not be smaller than dwarfs.