This is an introductory post to help users who want to create stunning technical documents in Word 2007. If you’ve typed Alt+= in Word 2007, you’ve seen a math-zone object inserted that says “Type equation here”. Actually you can type any mathematical expression there, even just a simple variable like x. If the expression's math zone is the only text in the paragraph, it'll be displayed in "display mode". Else it's displayed in the somewhat compressed "inline mode" as part of the paragraph (TeX's $$ vs $). As you type enough for an expression to be unambiguous, presto, it builds up right smack in front of your eyes! This process is called “formula autobuildup”, FAB for short, and expression ambiguity is determined by the UnicodeMath linear format documented in the Unicode Technical Note (UTN) http://www.unicode.org/notes/tn28/UTN28-PlainTextMath-v3.1.pdf. I recommend you read at least the introductory sections of this UTN. In general terms, formula autobuildup occurs whenever the user types a character that forces the text preceding the character to be the unambiguous linearly formatted text for a built-up expression as defined by the UTN. As such the character itself is not part of the resulting built-up expression. The UTN doesn’t state how already built-up objects are handled by the build-up code. For the most part, such expressions are just treated as parts of operands, but the build-up code does look inside some objects to see it they can be converted in some way. One example of this is that when a subscript object is being superscripted or a superscript object is being subscripted, the result is a subsup object. Try this kind of entry. It's the fastest way to enter equations that I've ever seen and I've been editing technical text ever since 1968.