I had a skype interview a few days after I filled the application. Less then one week, I was informed to take a on-site interview. The on-site interview followed the formal procedure, meeting with superviser and lab members one-by-one, giving a presentation for 1 hr, then talking with HR people. It took a whole day. About 3 days later, I was offered the position.

Whole day interview starting from 7:30am to 8pm. It was a combination of formal presentation, meeting PIs, lab members and HR for benefits. Breakfast with the PI, Lunch with other postdocs and students. The environment was very casual and it was not a super formal interview.