Intra- and inter-cellular information processing constitutes a defining characteristic of living systems. The “design” principles underlying the biological networks of cellular metabolism, genetic regulation, and cell-to-cell communication have become a major thrust of contemporary biology research, which aims to rationalize the efficiency and the robustness of biological networks in the light of form-function duality. Engineering efforts are underway to raise the precision and the accuracy of biochemical information processing to a level on a par with its silicon-based counterparts. Both of these efforts are closely linked to information theory and to the fundamental problems of equilibrium and nonequilibrium statistical mechanics. Here, we review the characteristics of biological circuits across different scales of time and space and in close comparison with man-made information processing systems.