I am a PhD candidate in the UBC Math Department; I study mathematical physics (i.e. the rigorous mathematical study of problems from physics), more specifically, quantum systems of many particles and their phase transitions.
That "click" when you come to understand a new concept - as in "ohhh, I get it!!!" - is one of the most beautiful and exciting feelings to me. There are few things in life that give me more satisfaction than helping another person to experience a "click".