Is it possible to construct artificial atoms and molecules that would perform quantum signal processing functions unattainable with natural ones? Superconducting microwave circuits serving as quantum bits illustrate the problem of engineering a controllable quantum electrodynamic system. A simple Lego-like set of three basic components - linear capacitances, linear inductances and non-linear Josephson inductances - can be combined with almost no limitations. Can circuit architecture mitigate or even eliminate decoherence due to defects of basic electrical constituents? This key questions will be discussed by reviewing the present entries of the "Mendeleev table" equivalent for superconducting circuits and known strategies for error corrections.