Casual, professional, informative, fun. During my interview day I met with HR to review some basic information and get a feel for the company and high level of the position. I then met with a panel of 3 individuals for an hour + who were super helpful in filling me in on the responsibilities of the position and had great challenging but not intimidating questions for me. I returned for an interview with the CTO and Director of HR, again very informative great sharing of information back and forth. I was then invited back for a job shadow - this was awesome and a great use of time for me to get a feel for the day to day and see how team mates interact with each other. Don't let this step put you off it's a fun couple of hours, take advantage of being able to spend that time with your prospective team, ask lots of questions and watch how team mates interact.