  Talk given at the 26th Workshop: ``From Superstrings to Supergravity", Erice
- Sicily, 5-12 December 1992. We review the superconformal properties of 2d
matter coupled to gravity, and extensions thereof. Focusing on topological
strings, we recall how the superconformal structure helps to provide a direct
link between Liouville theory coupled to matter, and matrix models. We also
construct an infinite class of new theories based on $W$-gravity.

High Energy Physics - Theory