First round is phone interview with an HR manager, they ask basic questions like why you’re interested in this position, what are your salary requirements. Second round is a 30 minute phone or video interview with your hiring manager, can be either more of an informal chat or rigorous technical interview. Last round is 3-4 hours of 30 minute long video interviews with a panel of employees ranging from entry-level to senior to Director level scientists in all research departments, not just the one you applied for. The questions asked and difficulty depends on who the interviewers are.