I found this interesting. Bob Levine pointed out in InDesign Magazine that Word’s DOCX file format is a glorified ZIP file.
“Change the extension to ZIP, unzip it, and you’ll find all of the document’s original assets, including the images as individual files in a folder. More importantly, InDesign can access the original high-resolution images when you place a DOCX file, even if they’re CMYK. The older DOC format converts all images to RGB PNG files.”