  The Yang-Lee edge singularity is a prototypical example of the application of
renormalization group ideas to critical behavior, and one to which Michael
Fisher made several important contributions. Moreover it has connections to
several other problems such as the statistics of branched polymers, and its
scaling limit in two dimensions provides a simple example of integrable field
theory. This article aims to give a pedagogical introduction to these matters,
with a few new ideas thrown in.
