The elementary excitations of a state of matter consisting of large collection of interacting particles can be very different from the original particles. In the most interesting examples, the particles effectively decompose into smaller constituent particles, which only carry a fraction of their quantum numbers. When these constituents are free, as in fractionally quantised Hall states, it is conceptually clear how to observe them. But what if they are confined, as it might be the case in spin liquids hypothesised to describe high Tc superconductors?

8 pages, 1 figure