One of the most difficult tasks in mathematical illustration is to add text to a figure - or maybe instead to add a figure to text. The problem is especially difficult in mathematics because even typsetting mathematics is not a trivial task.

Of course there is a canonical solution - to use TEX to format the text, and then somehow make it interact with the graphics program. There are many programs that do this, but most of them either don't do a great job of graphics or do not produce figures independent of the TEX environment.