Overview of Gravitational Critical Collapse*

The threshold of black hole formation in parametrized families of collapse models exhibits many of the features of a phase transition.  Universality and scaling behaviour are generically observed and a picture of critical phenomena emerges, completely analogous to that seen in statistical mechanical systems.

I will give an overview of developments in critical collapse over the past 30 years, starting with the original spherically symmetric massless scalar field study and culminating with some open questions that still occupy researchers.