Organized life is all about control. It's not enough to get a job done — it has to be done in the right place, at the right time and only under certain conditions. Control can be exerted in many different ways, and cells seem to have mastered all of them.

The simplest means of control is a switch that can be either on or off. In the cell, GTPases often act as molecular switches, and Johannes Bos and colleagues review on page 369how one of them, Rap1, regulates different processes, including migration, morphogenesis and cell adhesion.

Another approach is to create specialized compartments and restrict access to them. Intracellular organelles operate according to this principle, as they only allow the import of proteins that carry appropriate targeting signals. Protein import into mitochondria, chloroplasts and peroxisomes is reviewed in this issue by Klaus Pfanner and Andreas Geissler on page 339, Colin Robinson and Albert Bolhuis on page 350, and Vladimir Titorenko and Richard Rachubinski on page 357, respectively.

The force of inositol phosphates lies in their numbers — there could be more than 60 of them. The different forms have split up their tasks, and between them, they control myriad cellular processes. Robin Irvine and Michael Schell's review on page 327 will teach you all you need to know about these versatile second messengers.

Last, Michael Sheetz presents on page 392a more global approach to cell regulation based on physical control of mechanochemical processes involving the plasma membrane.

It's fine to be in control, but who actually does the work? Myosins apply force to create movement, and, on page 387, James Spudich describes the diverse approaches that have been used during the past 30 years to study this cellular workhorse.