The process consists on an initial quiz, a triage interview, 3 mentor interviews, and a final interview with the research manager. I found it to be a bit too much for an intern position, but I get they are very selective.

Did a test, passed. Then first-round technical interview on questions as mentioned in their letter to you. Then mentor interview. The interviewer was friendly and we had a good converasation, unfortunately I didn't pass it as he thinks that I was a bit inexperienced.