Systems biology has emerged as a highly interdisciplinary ?eld that has created broad enthusiasm in the scienti?c community. Systems biology is in vogue because of its potential to revolutionize not only biology but also medicine. Developments are anticipated that will change how we think about disease and how we approach therapeutic intervention. Perhaps the boldest vision of this future is presented by Dr. Leroy Hood, President of the Institute for Systems Biology in Seattle. He has been a protagonist and the main driving force of the underlying concept. - cording to Dr. Hood, systems biology will make possible a new era of medical care comprising predictive, preventive, personalized and part- ipatory (P4) medicine. While this vision appears futuristic, it has enticed both academic scienti?c communities and pharmaceutical industry R&D organizations. Systems biology ultimately attempts to understand biological s- tems at the molecular level. Examples of such systems are subcellular regulatory circuits with all their components, cells, organs, as well as - tire organisms. Over the past decade, technologies have been developed that enable systems-level interrogations, e.g., gene expression pro?ling, proteomics, and metabonomics, to name a few. Scientists have used such platforms to accumulate a tremendous amount of data. Although we have learned a great deal by collecting such detailed information, it seems our understanding has not similarly increased.