Most non-scientists will be aware that some cell types, such as cancer cells, spermatazoa and bacteria, can be far from sessile. Indeed, as outlined by Graham A. Dunn and Gareth E. Jones on page 667, such knowledge has existed for some time; possibly the first description of cell movement — that of microbes in tooth plaque — came from Antoni van Leeuwenhoek in 1683. Other relatively simple organisms can provide insight into cell movement in higher organisms. As Peter J. M. Van Haastert and Peter N. Devreotes describe on page 626, a simple amoeba has much in common with neutrophils in terms of the way it senses and responds to motile cues.

The concept that a cell within an epithelial structure such as the skin can move, however, might surprise many. Like the cells themselves, several of the proteins within them were thought to have a more structural role, simply conferring strength and rigidity to help carry out a 'barrier' function. A classic example of this is α-catenin, the functions of which, as Agnieszka Kobielak and Elaine Fuchs discuss on page 614, probably extend beyond simply connecting E-cadherin–α-catenin complexes to the actin cytoskeleton. Through other binding partners, α-catenin probably has roles in assembling this cytoskeleton and regulating its dynamics at cell–cell junctions. Similarly, actin-binding proteins were initially thought to just organize the cytoskeleton, but they are now known be involved in integrating cell structure with signal transduction, as outlined by Céline Revenu, Rafika Athman, Sylvie Robine and Daniel Louvard (page 635).

Why not explore the rest of this month's Focus issue and visit http://www.nature.com/nrm/focus/cytoskeletaldynamics for related content from across the Nature Publishing Group?