  We give a pedagogical introduction to the dynamics of N=2 supersymmetric
systems in four dimensions. The topic ranges from the Lagrangian and the
Seiberg-Witten solutions of SU(2) gauge theories to Argyres-Douglas CFTs and
Gaiotto dualities.
  This is a write-up of the author's lectures at Tohoku University, Nagoya
University and Rikkyo University. Comments will be appreciated.
