What's inside my car's muffler?

Some weird stringy stuff came out of my exhaust pipe today. I have no idea what it is. Could it be muffler guts? It’s creeping me out.

This link should help.

You don’t mention the age of the muffler, or what type of car it’s on. A SWAG makes me think it is fiberglass from the innards of a ‘glass pack’ style muffler.

Don’t know how old the muffler is, but the car is a 1994 Chevy Corsica.