How to see what Facebook groups your Facebook page is in? (Pages can join groups now)?

Go to any Facebook page, there would be a link called "Groups" in the side navigation bar. You can see a thing like "Groups this page has joined" or simliar block, all the joined Facebook groups are showed in this block of your Facebook page.

Also, all the pages can join any groups, just choose an identity (e.g. an user, a page) to join any groups when pressing the "join" button.