The actin cytoskeleton provides not only the underpinning for cell architecture but also mechanical force and the ability to drive movement of cells and their organelles. It is tempting to think of it simply as a set of stable structural elements, but nothing could be further from the truth. The cells of our bodies are continually remodelling their architecture by responding to a range of imposed biomechanical forces and intracellular functional demands. Studies of the dynamic and functional properties of the actin cytoskeleton have been dominated by a focus on actin and the view that actin filaments are essentially 'generic'. However, the 'other' component of most actin filaments in animals - tropomyosin - is coming into prominence. With this discovery is the realisation that far from being generic, actin filaments have their own functional individuality provided to them by their associated tropomyosin. This is changing the way we understand and study the actin cytoskeleton and has delivered a new therapeutic opportunity in what had come to be considered a 'no-go zone'.