I first interviewed with the head of HR for 30 minutes then I had 5 more interview sessions, each with a different pair of scientists and research associates. Each interview session was 30 minutes long and the entire process took 3 hours. I interviewed by myself with no other candidates. I had two phone interviews before I was called in for an on-site interview; the first interview was with the scientist in charge of the hiring for the position and the second interview was with the HR director and was much shorter than the first as they only asked basic questions (salary expectations, why did you leave your last job, will the commute be a problem, etc).