# Display custom field under image in TinyMCE editor

I have a custom media field called “Source” with the key `media_author`. I would like to display it under the image in the TinyMCE editor, like the caption field is:

The caption field is editable, but that’s not necessary for what I want to add. I found this code in `/wp-includes/js/tinymce/plugins/wpeditimage/plugin.js`. It looks like it’s part of how the caption is displayed.

``return '<div class="mceTemp"><dl id="' + id + '" class="wp-caption ' + align + classes + '" style="width: ' + width + 'px">' +        '<dt class="wp-caption-dt">'+ img +'</dt><dd class="wp-caption-dd">'+ caption +'</dd></dl></div>'; ``