I think that's great that you want to get into the field professionally. At the age of twelve I don't think you should worry about getting specific into any one area of the field. You realistically wont have to really focus until probably your sophomore year in college. Learn all you can about all areas of the field, keep your grades up and when you get into high school start identifying the colleges that have good programs for you area of interest at that time. Nowadays you can even start taking some college courses in high school that can give you a head start. Expose yourself to all aspects of the field. You may find your interests change the more you learn about other areas.