One phone interview that lasted almost an hour with the division chief I'd be assigned under and the mentor that would be working with me. Pretty standard fare, asked about myself, my interests and previous work, explained the organization and the work they did, what I would be doing there my first summer, gave me background on both of them. I was told that they would make their selection later that week and expect to hear from HR either way next week. HR phoned and gave a tentative verbal offer, followed by an official offer by email. Lots of paperwork ensued