I agree with sandiego's post about research. At a few of my interviews, I had to discuss my research in great depth. At one of them, I actually had to describe step-by-step an experimental technique, how many cells I plated, the different media I made & the ingredients, how I improved my experiments, what I could have done differently or better, even what concentrations of drugs worked better. (I did cancer research, and my interviewer was just fascinated with dose and kinetics dependent effects and their intricacies.)