Systems biology represents a paradigm shift from the study of individual genes, proteins or other components to that of the analysis of entire pathways, cellular, developmental, or organismal processes. Large scale studies, primarily initiated in Saccharomyces cerevisiae, have allowed the identification and characterization of components on an unprecedented level. Large scale interaction, transcription factor binding and phosphorylation data have enabled the elucidation of global regulatory networks. These studies have helped provide an understanding of cellular pathways and processes at a global and systems level.