One of the things that differentiates Smalltalk from a lot of the competing development systems is the full OO nature of it - everything is an object, and all the objects respond to messages. That extends all the way through the system, in ways that often surprise newcomers. For example - consider the creation of a new class - here's a screenshot of the browser:

That's the browser, and the text you see in the lower pane is actually a template for a message send - a keyword message that will create a new class (in the latest releases, there's a class creation dialog that simplifies this, but that's not my point here):

Smalltalk defineClass: #NameOfClass
	superclass: #{NameOfSuperclass}
	indexedType: #none
	private: false
	instanceVariableNames: 'instVarName1 instVarName2'
	classInstanceVariableNames: ''
	imports: ''
	category: 'Blog'

If you replace the templated sections with your own specifics, and then execute it, you'll get a new class. Why is that of interest?

Well, consider a runtime system that needs to interface to a database, with a need to bring in new kinds of domain objects on an ongoing basis. The runtime can create new classes on the fly, if that's how you want to deal with that. That may sound exotic, but I've got plenty of customers doing exactly that.