As technology continues to shrink we will eventually start building things, in a common manner, out of things we may not even be able to see. The Diamond Age is a great book about nanotechnology and, as is usual for Neal Stephenson, is packed with about three fun sci-fi ideas per page. And as we get better with the very small we will, inevitably, turn to nature for ideas. Why build a silicon filament when we can use an organic one? Why develop a gold-aluminium interface when cell membranes already have the desired properties? In case you can't tell, I am pulling these examples straight out of my nether interface. But the principle remains valid, as we need tools and pieces and machinery on a very small scale why not simply copy the organic blueprints that have proven themselves over millenia?
Which then leads to a blurry line between biology and engineering. Designed organisms that feed off of solar energy to light our roads at night. Genetically modified hair follicles that function as an interferometer. Whatever we can imagine, we will be able to make. We are approaching that day at a fairly good clip. We have surmounted physical limits at every turn of human history (irrigation, seafaring, flight, instant long-distance communication, etc.), and I see no reason why this will not continue at an increasing pace.
The question on my mind is not the hackneyed "What is it to be human?" but rather "What unimaginable wonder lies ahead of us?" Can you imagine showing a digital camera to an English peasant from the 15th century? What would early man make of an airplane? Will we be growing the Playstation 12? Will I be able to eat my credit card when it expires? There have always been things beyond the imagination of man (and always will be) and I'm amazed and enraptured by that which is beyond our current grasp but that I know we will eventually stumble upon. The world of a thousand years from now is sure to be so alien to me that it might as well come straight out of a fevered dream, a wonderful dream that I am living right now to the people from our distant past who could not begin to fathom what a blog might be.