I arrived in the morning, was given a visitor's badge, and briefly spoke with the President of the company. I gave a 50-minute talk, and was asked good questions by the audience. We had lunch (about 12 or so people), then the afternoon was spent in 1-on-1 interviews with four people relevant to the field to which I'd applied (physicists and engineers). Because I signed an NDA, I was allowed to briefly see the sorts of equipment they were developing. The day ended with a final discussion with the President. I received an offer soon after. The people I spoke with were all really sharp (top-tier) and very nice. The tech I saw was also top-of-the-line; similar to what you'd see at a university lab, but with better engineering.