Intracellular signaling: spatial and temporal control.

Cells integrate many inputs through complex networks of interacting signaling pathways. Systems approaches as well as computer-aided reductionist approaches attempt to "untangle the wires" and gain an intimate understanding of cells. But "understanding" any system is just the way that the human mind gains the ability to predict behavior. Computer simulations are an alternative way to achieve this goal--quite possibly the only way for complex systems. We have new tools to probe large sets of unknown interactions, and we have amassed enough detailed information to quantitatively describe many functional modules. Cell physiology has passed the threshold: the time to begin modeling is now.