Many biological systems, from the molecular scale to the macroscale and from the body to the brain, display remarkable efficiency and robustness. For example, a single mammalian cell, approximately 10 micrometers in size, performs complex biochemical signal processing on its mechanical and chemical input signals with highly noisy and imprecise parts, using approximately 1 picowatt (10−12 W) of power. Such signal processing enables the cell to sense and amplify minute changes in the concentrations of specific molecules amid a background of confoundingly similar molecules, to harvest and metabolize energy contained in molecules in its environment, to detoxify poisonous molecules, to sense if it has been infected by a virus, to communicate with other cells in its neighborhood, to move, to maintain its structure, to regulate its growth in response to signals in its surroundings, to speed up chemical reactions via sophisticated enzymes, and to replicate itself when it is appropriate to do so. The approximately 20,000-node gene-protein and protein-protein molecular network within a cell makes even the most advanced nano-engineering of today look crude and primitive.