📝What makes Smalltalk extensible?

Inspectable. You can expect any object in the system. You can look them up, sort, and search.

Self-contained. Most of the Smalltalk is implemented in Smalltalk. This allows looking at and changing any part of the system.

Simple universal metaphor. In Smalltalk everything is an object, and you can send a message to any object.

Dynamic, runs on VM. You don’t have to wait for the whole system to recompile when you introduce a change.