Found this Space Daily article detailing the latest in nano machines: muscle-powered robots. The first working example is apparently half the width of a human hair and is powered by the pulsing of some heart muscle. This represents a real breakthrough in how nanomachines are powered. Previous systems required electricity, while these simply need some glucose.

I fully believe that by the time my great-grandchildren are ready to buy a house, what they'll actually do is buy a plot of land, a mound of specially formulated dirt, a barrel of fluid and a bag of sand. The sand [micromachines] would be poured into the barrel [full of micromachine fuel], stirred up [activating the machines], and the barrel then poured on top of the dirt [full of the basic elements of all the construction materials]. A few days later in place of the dirt pile there would be a fully functioning house (perhaps right down to the electrics and HVAC).

Magic? Maybe. But even the most magic things start from tiny beginnings.