Interactions described by genetic and biochemical networks determine cellular properties and behaviors. Thus, understanding the design principles of biological networks has fundamental relevance to health, disease, and treatment of disease. A modular experimental system has been developed, in which genetic networks are synthesized in combinatorial manner. Different members of this network library vary in topology, but use the same components, making this system amenable to experimental and theoretical analysis. The proposed research will measure the internal network states over time as a prelude to developing a quantitative model of network dynamics. The library will also be used to explore the relationship between network topology and gene expression noise. Finally, since fluctuations in the concentration of components can lead to population heterogeneity, single cell analysis of network dynamics in response to time-varying inputs will be performed.