The University of Iowa has a two-tiered advising structure. Most entering undergraduate students are assigned to a professional academic advisor in the Academic Advising Center; students who are admitted directly to the College of Business, Engineering, or Nursing are assigned to an academic advisor in that college. The second tier is departmental or collegiate advising. Students are re-assigned to a professional or faculty advisor in their major department, typically after they have earned 24 semester hours of credit. Open Majors and students who plan to apply to a selective admission major will stay with their AAC advisor until they choose a major or are admitted to their major. Academic Advising Center advisors also advise pre-professional students throughout their undergraduate career, as they prepare for their application to graduate or professional school. These programs include Pre-Law, Pre-Medicine, Pre-Physical Therapy, and other pre-health programs.