I overheard a conversation in a class the other day about someone being able to "look" into various classes and data storage types and see what is being stored as you run the program.

I understand this can be done using the traditional ways of adding breakpoints and such, but the way the person was describing it seemed to be a lot more interactive. He mentioned "I can open a window for this class and monitor the data being stored in it". Does anyone know what he uses? I would have asked, but I haven't seen him again.

Thanks.