Easy to explore and modify. All the source code is available. The virtual machine side is more involved and I do not know how to do it. But on the Smalltalk side you can explore and change anything and everything. If you are used to using grep (find in files) to search for text strings in sources in other languages you can do something very similar in Smalltalk with ‘method source with it’ which will search for a given text string in the bodies of all methods in the system. It only takes a few seconds to search through all the methods. So anytime you want to know where in the sources a given string is used you can just go ahead and run a search. You get your answer in seconds. With this power comes responsibility. You can shoot yourself in the foot. If it breaks you get to keep both pieces. But you can easily start over.