A typical microprocessor integrates a large number (greater than a hundred million) of small (less than 100 nanometers) electronic parts, but the miniaturized systems of the future will also need to incorporate photonic, mechanical, chemical, and even biological devices. The semiconductor industry has had impressive success in producing integrated electronics, but it has been decidedly less successful at mass-manufacturing multifunctional microsystems, partly because the processes used to make different components are incompatible. A major question for engineers is what manu­facturing process can mass-­produce useful multi­functional, miniature systems. The conventional approach to making engineered products is unlikely to yield a satisfying answer.

The most complex functional systems are found in the biological world. Nature is full of machines with trillions of nanoscale components all working in harmony. The complexity and sophistication of biological machines--in terms of the number of parts, the variety of materials used, and the diversity of functions performed--is far beyond what any microfabrication or nanofabrication can achieve.