I applied through university. The process took 2 months. I interviewed at 3M in Nov 2016
Interview
I talked to 3M at a campus recruiting event, applied online, and a few weeks later got asked to participate in a phone interview. The interview lasted about an hour and had very straight-forward questions that were mostly about my resume-- they wanted to know about my past experiences in internships and what I was involved in on campus. There weren't really any behavioral questions.
Interview questions [1]
Question 1
What is one big thing you took away from your previous internships?