Directly Manipulating Open Xml
You can directly embed an Excel spreadsheet in a Word document. A document that has a spreadsheet embedded in it has a specific structure. This screen-cast explores this structure, shows how you can take the DOCX apart, then take the embedded XLSX apart, modify the markup in the XLSX, then re-zip the XLSX, then re-zip the DOCX. Along the way, I explore the issue of updating the image that Word displays by default for the spreadsheet.