Debugging in Smalltalk

I heard that Smalltalk provides a very good debugging environment. I am surprised and I want to know what's special about Smalltalk that has made it’s so popular. Any insight on this would help.

Small talk has a graphical debugging environment and the Smalltalk debugger is a powerful tool. The debugging environment provides a 'stack trace' which gives a short history list of the current error condition. It is also possible to highlight lines during trace event in order to view the code and active variables. If one highlights the variables then it gives information about the current value of variables.