PhD students in Dan Mulvihill’s group have recently published a study in which they have uncovered the mechanism by which the physical properties of different populations of actin filaments within cells are fine tuned to undertake different functions (http://dx.doi.org/10.1016/j.cub.2014.05.034). While some of these actin polymers are “fine-tuned” to provide a stable scaffold or framework to the cell, others are more dynamic and allow the cell to rapidly respond to changes in its environment. Matt Johnson and Dan East used a novel molecular biology trick to change the cellular location of different formin “nucleators” which seed actin filament growth. They discovered this led to a switch in the location of molecules which bind to and stabilise the actin polymer and modulate the movement of molecular motors. In this way they uncovered the mechanism which determines the functional characteristics of actin filaments in all cells and orchestrates cellular events in organisms from yeast to man. These findings are likely to have a major impact in the development of therapies for a variety of diseases, such as cancer.