How to get object's parent?

How to get object's parent?

Hi,
please take a look at the following source,
  1. jQuery.fn.extend({     
  2.     colorbox : function (option) {
  3.         // do some thing;
  4.     };
  5. });
  6. var cb = jQuery.colorbox = {
  7.     c : {},
  8.     obj: {
  9.         self: function(){
  10.             //get div object who called like this: $(div).colorbox();
  11.         }
  12.     }
  13. };
This is a plugin Some uncertain div would call colorbox() to make a colorbox. Then, how to get this div object in self() function?