Outside The Box
PhD researchers have to be creative in some way: a candidate is expected to produce a significant and original contribution through their work.
What makes your work original? In what ways were you creative throughout your PhD? How did you look at things differently? How did you find solutions to problems?
What did you do that no-one has ever done before?
And having stepped out of one box through your work, what does the new box look like?
(and how might you or someone else go further?)