I am starting a postdoc in Materials, and have spoken to a head of school about a planning for a 5 year fellowship after that will lead onto a lecturing role. Problem is, now I have to work out what I am going to be an expert in. How did you guys get your ideas for research interests? Was it just continuing your PhD work? Did you specifically seek out boundary cases between disciplines? Look at the business section of the newspaper? Chase where the funding was?