One round in-person. It was mostly behavioral questions but if you're a junior they will probably ask slightly more technical questions. There were two people interviewing me and overall, it was a pretty smooth, straightforward process.
Le processus a pris 1 jour. J'ai passé un entretien chez 3M (Saint Paul, MN) en oct. 2011
Entretien
I went in to an on-campus interview. I went to a pre-night where three employees/interviewers gave a presentation on the interview and internship process at 3M. Although the interview wasn't extremely hard, they did ask questions that kept me on my toes. Make sure you are up-to-date on all of the companies operations.