First round is with current fellows, second round is with the specific team you applied for (i.e. analytics, project management/program support, etc.), and third round is with a higher up. The application required all pretty standard components to a fellowship/grad school program (i.e. personal statement, references, transcript).
Overall got a hierarchical feel after my second interview. It's hard to say how much input you would get to offer at the organization, despite the small size. It seemed as though the role required fellows to carry out the agenda already planned for versus developing your own interests to take on your own projects as a post-baccalaureate fellow. Ultimately was not a good fit.