AUCTeX is an extensible package for writing and formatting TeX files
in GNU Emacs and XEmacs. It supports many different TeX macro packages,
including AMS-TeX, LaTeX, Texinfo, ConTeXt, and docTeX (dtx files).
AUCTeX includes preview-latex which makes LaTeX a tightly integrated
component of your editing workflow by visualizing selected source chunks
(such as single formulas or graphics) directly as images in the source