We review experimental work on a protein called Dishevelled. The unusual name derives from the fact that some mutations in Dishevelled cause fruit flies to develop with misaligned hairs on their bodies. Dishevelled apparently phase separates inside the cytosol of cells. As mutant variants of this protein that cannot phase separate also cannot perform their biological function, phase separation appears to be functional. The mechanism by which Dishevelled functions is poorly understood. We suggest that physical scientists may be able to contribute to the effort to understand how Dishevelled functions, by applying their knowledge of phase separation behaviour. We start to do this by comparing the predictions of a simple model of phase separation to the experimental data.