Particle tracking systems have been used in experimental mechanics for nigh on 40 years. The technique originated in the domain of fluid mechanics, where it was typically referred to as particle tracking velocimetry (PTV), but it has spread to other domains such as structural engineering in the intervening years. Conceptually the technique is refreshingly simple. Some material, whether solid, fluid or gaseous is “marked” in some way and modern image capture equipment, typically a digital camera of some sort, is employed to record the motion of those marks (particles) through time. Finally, the recorded images are analysed by a suitable software tool to extract physically meaningful quantities such as material displacement or velocity, or some quantity derived from these variables, such as vorticity or strain. One of the attractions of particle tracking systems is that “what you see is what you get”. There are no sophisticated electronics behind the scenes processing electrical signals coming from a sensor of some sort. Instead, a set of physical objects – the particles – move through space and their motion not only generates the variables of interest, but provides the experimenter with a highly visual record of the material’s actual behaviour.