There were two parts to the interviewing process. First was an initial phone interview with a representative currently working for the foundation where they gauged your aptitude for global health work and which teams you would best be suited for. Once passing that, you moved on to a 1:1 interview with the heads of each of the teams they recommended you for. It is the team heads that ultimately offer you a position. I definitely recommend coming prepared with relevant and thoughtful questions since your passion for the subject will set you apart in a pool where everyone has the same education.