I got email from the recruiter shortly after my friend in Facebook referred me. The recruiter asked me a few basic questions in the phone and arranged a phone interview. The phone interview took about 1 hour and the interviewer asked two questions. Shortly after that they told me to have an on-site interview in their campus. The on-site interview is 1-on-1 and the interviewer asked me two questions that is of average difficulty. But it is very important to communicate your solution clearly to the interviewer. Then within one week, I got the internship offer from Facebook.