Labour law has always been preoccupied with boundaries. One can either be an 'employee' or not, an 'employer' or not, and the answer dictates who comes within the scope of labour law, for better or worse. But such divisions have always been difficult, and in recent years their shortcomings have become ever more pronounced. The proliferation of new work arrangements and heightened global competition have exposed a world-wide crisis in the regulation of work. It is therefore timely to re-assess the idea of labour law, and the concepts, in particular the age-old distinctions - that are used to delimit the field. This collection of essays, by leading experts from around the world, explores the frontiers of our understanding of labour law itself.