How do I transfer contacts from my Z10 to the Nexus S ?

I got my Z10 for a year now, and transferring contacts to it was pretty simple from the previous iPhone that I had, now I want to transfer Contacts from my Z10 to a new phone I got : Google Nexus S but I've no idea how and couldn't find anything on google...

anyone here has a clue how to do it ?

Thanks!