Microswimmers are spontaneously moving droplets that can mimic much of the behaviour of simple forms of life, such as swarming, flocking and chemotaxis, in an abiotic system. This project focusses on oil-in-water micro-swimmers, which are self-propelled droplets of liquid crystal. Their motions are powered by the gradual transfer of oil into surfactant micelles, which then swell in size. However, several such transport mechanisms are possible: a direct observation of the size-distribution of micelles would allow discrimination between these mechanisms, and quantification of e.g. their reaction kinetics. Our aim is to achieve such direct measurement with SAXS of a the time-evolution of micelles in a diffusive boundary layer above a well-defined oil-water interface. This would settle the question of why these micro-swimmers actually swim, and allow for exploration of new physics with these systems by the rational design of their properties.