Today I met Heisuke Hironaka, the great mathematician famous for his proof of resolution of singularities in characteristic zero. His solution remains among the greatest pieces of mathematical work ever. Grothendieck, arguably the greatest ever algebraic geometer, is said to have claimed (orally) that "Hironaka's work is the most complicated mathematical work".
He is also a Fields medalist. (Fields medal is the biggest award there is for mathematicians.) In fact he becomes the first Fields medalist I met or saw in my life!
When my adviser introduced me to him today, the amusing dialogue went something like this:
I: Very nice to meet you, Sir.
Hironaka: Nice to meet you. Nice to meet young geniuses. [To Bernard Tessier who was present] they don't know now that they are geniuses....they will know in future.
He appeared old, but was quite lively. He is supposed to give some talks in the conference, and he asked the organizers to schedule his talks in the afternoon, because "I feel weak in the mornings. You know my grand mother used to take half an hour to get down from the bed. I am becoming like her"!