Consisted of five (5) interviews: one phone screen, one interview with the team software architect, two interviews with senior team members (PhD physicists), and one mostly personality interview. All fairly professional, however I was a bit taken aback by the interviews with the senior team members. They asked almost strictly theoretical questions from undergrad physics and numerical analysis -- nothing applied.
The recruiter I worker with was positively awful, however. Took over a month from date of intention to make me an offer to the first verbal offer. Written offer maybe two weeks after that.