What should I wear to my interview?

Just dress as a professional. Not necessarily a suit or formal work attire but as you did to get original interview. Avoid gaudy jewelry, unkempt hair and so forth and be prepared to answer their questions honestly. As long as you look respectable you should be fine for the interview, don't stress over your hair up or down, it won't matter here as this is just an interview and if hired they will tell you their requirements for appearances while working. Good Luck!!!