Abstract: The best-studied signaling pathways still hold secrets. Recent studies have now applied a new wave of technologies encompassing computational approaches and experimental techniques to the mitogen-activated protein kinase pathway in yeast and have provided new knowledge of pathway connections, components, and dynamics. The computational algorithms build on advances in network science motivated by studies of large-scale social and WWW networks. Experimental techniques permit exploration of the frequency-space response, describing biological signaling networks in the language of control theory. Together, these technologies are revealing the design choices made by evolution, and they provide a framework for building new biological circuits to order.