Basically just conversations with a few faculty about science and research. They talk to you about what their lab works on, and you ask questions about their work. Then you talk about what you've worked on in your previous projects.
Not very hard, just some simple question about your resume and self introduction, professors will choose the candidates who have relevant experience. Also they will consider about the time you can contribute to the project. They are very friendly.
Interview questions [1]
Question 1
Tell me something about your past experience in XX
Generic grad school interview process. You chat with the PI that you are interested in. They ask you about your undergrad research experience and they introduce what they are currently working on. They also ask your current research interest.
Interview questions [1]
Question 1
Talk about past research experiences and future research interest.