I had met several employees and the CEO previously on a couple occasions. At one point I simply inquired about possible internships in the future, which turned into email conversations to get a date for the interview, which turned into a pleasant walk to lunch with the interview taking place both on the walk and at the destination. The interviewers (two briefly then one was called away) were very knowledgeable. They inquired about past experience, knowledge/skills, the usual. Then they presented me with a few possible projects, asking which I would be interested in.