4D N=2 theories exhibit a rich structure of RG flows between UV and IR SCFTs. With G. Elliot, M.J. Kang and C. Lawrie, we have been this structure of RG flows from a variety of perspectives. In this talk, I would like to focus on the Vertex Operator Algebra (VOA) that can be associated to a 4D N=2 SCFT, and what these VOAs can tell us about the Higgs Branch RG flow between these theories.

I'll give an introduction to N=2, D=4 SCFTs of "Class-S" and a survey of our programme for classifying such theories. I will put special emphasis on the theories arising from the Exceptional (2,0) SCFTs in D=6.