Myriad molecules in motion: simulated diffusion as a new tool to study molecular movement and interaction in a living cell.

The molecular study of life is in the midst of a challenging transformation. Information and insights gained from characterization of individual cellular components have established a platform from which to take the next step, i.e., to address molecular activity in a living cell. In a cell, spatial localization, limited numbers of molecules, and molecular crowding define an environment unlike that of a test tube. To delve successfully into this new world, we need new tools, some of which will certainly be computational. A fascinating first application of such a tool is described in this issue of the Journal of Bacteriology by Lipkow et al. (9).