Two technical interviews with research PIs. Both were quite friendly and relaxed. The interviewer were positive and tried to help me respond the questions in case I didn't know the answer.

I found the job through my personal/professional network. I discussed with my hiring manager before submitting my resume to HR. HR then scheduled an on-site interview. I started by giving a presentation to the whole group on my background. The interview was most of a day (10-4) and they took me to lunch as a team. I was interviewed by about 6 people, who asked a wide variety of questions. Some basic questions about my technical background and simple coding were asked, but no significant brain teasers. The atmosphere was one of mutual respect. I felt that both parties were feeling out a personality fit as much as for technical competency.