I applied via an internal referral and the first round is an 1-hour phone interview. As I was a PhD candidate, I was asked to give a 30-40 minute talk of my research work. I sent them my slides before the talk, and during the interview we went over the slides on each side respectively. I was interviewed by a team of 3 PhD scientists, with solid quantitative background. The talk was less formal than a regular academic talk, and more like briefing my work to them. They asked many clarification questions throughout my talk, so it is quite casual. After the phone interview I was told (via my internal referrer) that they had a positive impression. Their movement is quite slow: 4 weeks after the interview that they formally asked me to the on-site interview.