By revealing the set of ~23000 genes that guide human biology, genomics has identified many of the components that are involved in various biological systems. However, it is clear that life cannot be understood as the simple action of the component parts alone. The behaviour and function of signaling pathways, cells, organs and organisms is likely to depend not only on the presence of the component parts, but also on the interactions between them. In many cases the properties of the system could not be predicted from studying a single component alone. Systems biology is an approach that analyses all of the components, interactions and dynamics of a biological system in a quantitative and integrative fashion. This change in perspective has led to a resurgence of interest in adopting approaches common other sciences, such as computing, engineering, mathematics and physics, in which theory, modeling and experiment are combined in order to understand and predict the behaviour of a complex system.