Show all changed field values

Hi experts,

I have created a workflow for converting an opportunity into a project. During an opportunity's life cycle there are various stages such as:

My quote can be made into a project when it is in stages: commitment received, deposit received, and closed (won).

So lets assume we are in the deposit received stage in which case the workflow is triggered an a project for the quote record is also created. Now if a user makes some changes in the fields of the opportunity, I would a workflow to be triggered to send an email which contains all the fields that were changed. How can I capture all this info?

Thanks,

Jon